[clang] [llvm] [clang] Add regalloc PBQP for all targets in clang (PR #166645)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 130601 tests passed
* 2925 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang
<details>
<summary>Clang.CodeGen/PBQP-regalloc-all-targets.c</summary>

```
Exit Code: 1

Command Output (stdout):
--
# shell parser error on RUN: at line 1: c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc C:\_work\llvm-project\llvm-project\clang\test\CodeGen\PBQP-regalloc-all-targets.c -triple x86_64 -O2   -mllvm -regalloc=pbqp   -mllvm --print-changed -S |& c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe C:\_work\llvm-project\llvm-project\clang\test\CodeGen\PBQP-regalloc-all-targets.c

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/166645