This relands changes in #144424 for adding a count of DWO files
parsed/loaded and the total number of DWO files.

The previous PR was reverted in #145494 due to the newly added unit
tests failing on Windows and MacOS CIs since these platforms don't
support DWO. This change add an additional
`@add_test_categories(["dwo"])` to the new tests to
[skip](https://github.com/llvm/llvm-project/blob/cd46354dbd10820158edabe14dbd49d9f9010722/lldb/packages/Python/lldbsuite/test/test_categories.py#L56)
these tests on Windows/MacOS.

Original PR: #144424

### Testing
Ran unit tests
```
$ bin/lldb-dotest -p TestStats.py llvm-project/lldb/test/API/commands/statistics/basic/
----------------------------------------------------------------------
Ran 24 tests in 211.391s

OK (skipped=3)
```

Reverts llvm/llvm-project#144424

Caused CI failures.

macOS CI failure was:
```
10:20:36  FAIL: test_dwp_dwo_file_count (TestStats.TestCase)
10:20:36      Test "statistics dump" and the loaded dwo file count.
10:20:36  ----------------------------------------------------------------------
10:20:36  Traceback (most recent call last):
10:20:36    File "/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/llvm-project/lldb/test/API/commands/statistics/basic/TestStats.py", line 639, in test_dwp_dwo_file_count
10:20:36      self.assertEqual(debug_stats["totalDwoFileCount"], 2)
10:20:36  AssertionError: 0 != 2
10:20:36  Config=arm64-/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/bin/clang
10:20:36  ======================================================================
10:20:36  FAIL: test_no_debug_names_eager_loads_dwo_files (TestStats.TestCase)
10:20:36      Test the eager loading behavior of DWO files when debug_names is absent by
10:20:36  ----------------------------------------------------------------------
10:20:36  Traceback (most recent call last):
10:20:36    File "/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/llvm-project/lldb/test/API/commands/statistics/basic/TestStats.py", line 566, in test_no_debug_names_eager_loads_dwo_files
10:20:36      self.assertEqual(debug_stats["totalDwoFileCount"], 2)
10:20:36  AssertionError: 0 != 2
10:20:36  Config=arm64-/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/bin/clang
10:20:36  ======================================================================
10:20:36  FAIL: test_split_dwarf_dwo_file_count (TestStats.TestCase)
10:20:36      Test "statistics dump" and the dwo file count.
10:20:36  ----------------------------------------------------------------------
10:20:36  Traceback (most recent call last):
10:20:36    File "/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/llvm-project/lldb/test/API/commands/statistics/basic/TestStats.py", line 588, in test_split_dwarf_dwo_file_count
10:20:36      self.assertEqual(len(debug_stats["modules"]), 1)
10:20:36  AssertionError: 42 != 1
10:20:36  Config=arm64-/Users/ec2-user/jenkins/workspace/llvm.org/as-lldb-cmake/lldb-build/bin/clang
```

## Summary
A new `totalLoadedDwoFileCount` and `totalDwoFileCount` counters to
available statisctics when calling "statistics dump".

1. `GetDwoFileCounts ` is created, and returns a pair of ints
representing the number of loaded DWO files and the total number of DWO
files, respectively. An override is implemented for `SymbolFileDWARF`
that loops through each compile unit, and adds to a counter if it's a
DWO unit, and then uses `GetDwoSymbolFile(false)` to check whether the
DWO file was already loaded/parsed.

3. In `Statistics`, use `GetSeparateDebugInfo` to sum up the total
number of loaded/parsed DWO files along with the total number of DWO
files. This is done by checking whether the DWO file was already
successfully `loaded` in the collected DWO data, anding adding to the
`totalLoadedDwoFileCount`, and adding to `totalDwoFileCount` for all CU
units.

## Expected Behavior
- When binaries are compiled with split-dwarf and separate DWO files,
`totalLoadedDwoFileCount` would be the number of loaded DWO files and
`totalDwoFileCount` would be the total count of DWO files.
- When using a DWP file instead of separate DWO files,
`totalLoadedDwoFileCount` would be the number of parsed compile units,
while `totalDwoFileCount` would be the total number of CUs in the DWP
file. This should be similar to the counts we get from loading separate
DWO files rather than only counting whether a single DWP file was
loaded.
- When not using split-dwarf, we expect both `totalDwoFileCount` and
`totalLoadedDwoFileCount` to be 0 since no separate debug info is
loaded.

## Testing
**Manual Testing**
On an internal script that has many DWO files, `statistics dump` was
called before and after a `type lookup` command. The
`totalLoadedDwoFileCount` increased as expected after the `type lookup`.
```
(lldb) statistics dump
{
  ...
  "totalLoadedDwoFileCount": 29,
}
(lldb) type lookup folly::Optional<unsigned int>::Storage
typedef std::conditional<true, folly::Optional<unsigned int>::StorageTriviallyDestructible, folly::Optional<unsigned int>::StorageNonTriviallyDestructible>::type
typedef std::conditional<true, folly::Optional<unsigned int>::StorageTriviallyDestructible, folly::Optional<unsigned int>::StorageNonTriviallyDestructible>::type
...
(lldb) statistics dump
{
  ...
  "totalLoadedDwoFileCount": 2160,
}
```
**Unit test**
Added three unit tests that build with new "third.cpp" and "baz.cpp"
files. For tests with w/ flags `-gsplit-dwarf -gpubnames`, this
generates 2 DWO files. Then, the test incrementally adds breakpoints,
and does a type lookup, and the count should increase for each of these
as new DWO files get loaded to support these.
```
$ bin/lldb-dotest -p TestStats.py ~/llvm-sand/external/llvm-project/lldb/test/API/commands/statistics/basic/
----------------------------------------------------------------------
Ran 20 tests in 211.738s

OK (skipped=3)
```

As discussed with @DavidSpickett in discord. Running the test runner
caused the following issue:

```
gmake: Entering directory '/home/kper/oss/llvm-project/build/lldb-test-build.noindex/functionalities/thread/concurrent_events/TestConcurrentSignalWatch.test'
/home/kper/oss/llvm-project/build/bin/clang++  -std=c++11 -g -O0  -mriscv -I/home/kper/oss/llvm-project/lldb/packages/Python/lldbsuite/test/make/../../../../..//include -I/home/kper/oss/llvm-project/build/tools/lldb/include -I/home/kper/oss/llvm-project/lldb/test/API/functionalities/thread/concurrent_events -I/home/kper/oss/llvm-project/lldb/packages/Python/lldbsuite/test/make -include /home/kper/oss/llvm-project/lldb/packages/Python/lldbsuite/test/make/test_common.h -fno-limit-debug-info      --driver-mode=g++ -MT main.o -MD -MP -MF main.d -c -o main.o /home/kper/oss/llvm-project/lldb/test/API/functionalities/thread/concurrent_events/main.cpp
clang++: error: unknown argument: '-mriscv'
gmake: *** [Makefile.rules:619: main.o] Error 1
```

By overriding the flags, we avoid the `-mriscv`.

With this patch, vector registers can be read and written when debugging a live process.

Note: We currently assume that all LoongArch64 processors include the
LSX and LASX extensions.

To add test cases, the following modifications were also made:
lldb/packages/Python/lldbsuite/test/lldbtest.py
lldb/packages/Python/lldbsuite/test/make/Makefile.rules

Reviewed By: DavidSpickett, SixWeining

Pull Request: https://github.com/llvm/llvm-project/pull/120664

Got caught out by this because simply specifying `DYLIB_CXX_SOURCES`
(without specifying `DYLIB_NAME`) resulted in linker errors because the
dylib was never built (and linked). We should probably make that a
Makefile error (though I haven't audited when exactly not specifying
`DYLIB_NAME` is valid; looked like that can happen when we specify
`FRAMEWORK`).

This fix is based on a problem with cxx_compiler and cxx_linker macros
on Windows.
There was an issue with compiler detection in paths containing "icc". In
such case, Makefile.rules thought it was provided with icc compiler.

To solve that, utilities detection has been rewritten in Python.
The last element of compiler's path is separated, taking into account
the platform path delimiter, and compiler type is extracted, with regard
of possible cross-toolchain prefix.

---------

Co-authored-by: Pavel Labath <pavel@labath.sk>

@walter-erquinigo found the the [PR with testing and a fix for
DebugInfoD](https://github.com/llvm/llvm-project/pull/98344) caused an
issue when working with stripped binaries.

The issue is that when you're working with split-dwarf, there are *3*
possible files: The stripped binary the user is debugging, the
"only-keep-debug" *or* unstripped binary, plus the `.dwp` file. The
debuginfod plugin should provide the unstripped/OKD binary. However, if
the debuginfod plugin fails, the default symbol locator plugin will just
return the stripped binary, which doesn't help. So, to address that, the
SymbolVendorELF code checks to see if the SymbolLocator's
ExecutableObjectFile request returned the same file, and bails if that's
the case. You can see the specific diff as the second commit in the PR.

I'm investigating adding a test: I can't quite get a simple repro, and
I'm unwilling to make any additional changes to Makefile.rules to this
diff, for Pavlovian reasons.

These changes aim to support cross-compilation build on Windows host for
Linux target for API tests execution. They're not final: changes will
follow for refactoring and adjustments to make all tests pass.

Chocolatey make is recommended to be used since it is maintained better
than GnuWin32 mentioned here
https://lldb.llvm.org/resources/build.html#windows (latest GnuWin32
release is dated by 2010) and helps to avoid problems with building
tests (for example, GnuWin32 make doesn't support long paths and there
are some other failures with building for Linux with it).

Co-authored-by: Pavel Labath <pavel@labath.sk>

In MinGW make, the `%windir%` variable has a lowercase name `$(windir)`
when launched from cmd.exe, and `$(WINDIR)` name when launched from
MSYS2, since MSYS2 represents standard Windows environment variables
names in upper case.

This commit makes Makefile.rules consider both run variants.