Linux has a limitation of 256 characters for a path. Large function
names being serialized will cause this to fail. As createTemporaryFile
already unique's the file (up to 128 retries for different name
variations), truncating should suffice

Depending on the CMake configuration, these missing headers triggers a
compilation error.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

The build was broken when MLIR_NVVM_EMBED_LIBDEVICE was enabled.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

When enabling or disabling a target we typically need to rebuild most
of LLVM because of the change to the values of the LLVM_HAS_*_TARGET
macros in llvm-config.h, which is included by most of the code, but
are unused by LLVM itself. To avoid this, move the LLVM_HAS_*_TARGET
macros to a separate header, Targets.h.

Update the only in-tree user of the macros (MLIR) to refer to the new
header. I expect that out-of-tree users will detect the change either
at compile time if they build with -Wundef, or at runtime. As far as
I can tell, the usage of these macros is rare in out-of-tree projects,
I found no out-of-tree users in projects indexed by Debian code search
[1], and one user [2] in projects indexed by GitHub code search [3]
(excluding forks of LLVM).

[1] https://codesearch.debian.net/search?q=%23.*LLVM_HAS_.*_TARGET&literal=0
[2] https://github.com/AndreyPavlenko/graph-compiler/blob/238706b12b63945dc490f9f5f33a2d20b3c58944/lib/gc/Target/LLVM/XeVM/Target.cpp#L72
[3] https://github.com/search?q=%2F%23.*LLVM_HAS_.*_TARGET%2F&type=code

Reviewers: nico, grypp, mstorsjo, MaskRay

Reviewed By: MaskRay

Pull Request: https://github.com/llvm/llvm-project/pull/136388

As title, we need to call `Timer::clear` to avoid extra log like this:
```
===-------------------------------------------------------------------------===
                           ...
===-------------------------------------------------------------------------===
  Total Execution Time: 0.0000 seconds (0.0000 wall clock)

   ---Wall Time---  --- Name ---
        -----       ....
        -----       Total
```

PTX source files are expected to only contain ASCII text
(https://docs.nvidia.com/cuda/parallel-thread-execution/#source-format) and no null terminators.

`ptxas` has so far not enforced this but is moving towards doing so.
This revealed a problem where the null terminator is getting printed out
in the output file in MLIR path when outputting ptx directly. Only add the null on the assembly output path for JIT instead of in output of `moduleToObject `.