These changes slighly modify the output of the unittests so that they better
match GTest, so that utilities that parse the expected output from GTest (such
as Android's unit test harness) can read the output from our unit tests.

This allows our unit tests to be run on Android devices.

Add very primitive command line parsing to:
- support --gtest_color=no to disable printing terminal colors.
- recognize --gtest_print_time and print the test time in milliseconds.
  - most of our unit tests run on the order of microseconds, so its useful to
    preserve the existing behavior.  But upsteram GTest ONLY prints time tests
    in milliseconds, and Android's atest expects to be able to parse exactly
    that. Atest always passes --gtest_print_time. The word `took` is removed as
    that also differs from upstream GTest, tripping up parsers.
- ignore other --gtest_* flags

Do so so that atest can parse the output correctly.

Print the test number count before
each run, so that atest can parse this value correctly.

Link: https://android-review.googlesource.com/c/platform/external/llvm-libc/+/3107252
Link: https://google.github.io/googletest/advanced.html#colored-terminal-output
Link: https://google.github.io/googletest/advanced.html#suppressing-the-elapsed-time

Summary:
There are a lot of random training spaces on various lines. This patch
just got rid of all of them with `sed 's/\ \+$//g'.

Summary:
This is a massive patch because it reworks the entire build and
everything that depends on it. This is not split up because various bots
would fail otherwise. I will attempt to describe the necessary changes
here.

This patch completely reworks how the GPU build is built and targeted.
Previously, we used a standard runtimes build and handled both NVPTX and
AMDGPU in a single build via multi-targeting. This added a lot of
divergence in the build system and prevented us from doing various
things like building for the CPU / GPU at the same time, or exporting
the startup libraries or running tests without a full rebuild.

The new appraoch is to handle the GPU builds as strict cross-compiling
runtimes. The first step required
https://github.com/llvm/llvm-project/pull/81557 to allow the `LIBC`
target to build for the GPU without touching the other targets. This
means that the GPU uses all the same handling as the other builds in
`libc`.

The new expected way to build the GPU libc is with
`LLVM_LIBC_RUNTIME_TARGETS=amdgcn-amd-amdhsa;nvptx64-nvidia-cuda`.

The second step was reworking how we generated the embedded GPU library
by moving it into the library install step. Where we previously had one
`libcgpu.a` we now have `libcgpu-amdgpu.a` and `libcgpu-nvptx.a`. This
patch includes the necessary clang / OpenMP changes to make that not
break the bots when this lands.

We unfortunately still require that the NVPTX target has an `internal`
target for tests. This is because the NVPTX target needs to do LTO for
the provided version (The offloading toolchain can handle it) but cannot
use it for the native toolchain which is used for making tests.

This approach is vastly superior in every way, allowing us to treat the
GPU as a standard cross-compiling target. We can now install the GPU
utilities to do things like use the offload tests and other fun things.

Some certain utilities need to be built with 
`--target=${LLVM_HOST_TRIPLE}` as well. I think this is a fine
workaround as we
will always assume that the GPU `libc` is a cross-build with a
functioning host.

Depends on https://github.com/llvm/llvm-project/pull/81557

This is step 4 of
https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079

The previous patches added the necessary support for global constructors
used to register tests. This patch enables the NVPTX target to build
and run the unit tests on the GPU. Currently this only tests the ctype
tests, but adding more should be straightforward from here on.

This ran all the ctest unit tests when run on an sm_70.

Depends on D149517 D149527

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D149532

Previously, only those unit tests which belonged to a suite were run as
part of libc-unit-tests. It meant that unit tests not part of any suite
were not being tested. This change makes all unit tests run as part of
libc-unit-tests. The convenience function to add a libc unit test suite
has been removed and add_custom_target is used in its place. One of the
bit-rotting test has along been fixed. Math exhaustive and differential
tests are skipped under full build.

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D148784

This part of the effort to make all test related pieces into the `test`
directory. This helps is excluding test related pieces in a straight
forward manner if LLVM_INCLUDE_TESTS is OFF. Future patches will also move
the MPFR wrapper and testutils into the 'test' directory.

Previously, the entire support/CPP folder was in one header library,
which meant that a lot of headers were included where they shouldn't be.
This patch splits each header into its own target, as well as adjusting
each place they were included to only include what is used.

Reviewed By: sivachandra, lntue

Differential Revision: https://reviews.llvm.org/D121237

The idea is to move all pieces related to the actual libc sources to the
"src" directory. This allows downstream users to ship and build just the
"src" directory.

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D112653

This addition reads command line input to run specific single tests
within a larger call to run all the tests for a particular function.
When the user adds a second argument to the command line, the code skips
all the tests that don't match the user's specified binary. If the user
doesn't specify a test correctly and/or no tests are run, a failure
message prints.

Reviewed By: sivachandra, aeubanks

Differential Revision: https://reviews.llvm.org/D105843