[llvm] Adding Separate OpenMP Offloading Backend to `libcxx/include/__algorithm/pstl_backends` (PR #66968)

[Louis Dionne via llvm-commits]

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@@ -330,6 +330,23 @@ def getStdFlag(cfg, std):
         default=f"{shlex.quote(sys.executable)} {shlex.quote(str(Path(__file__).resolve().parent.parent.parent / 'run.py'))}",
         help="Custom executor to use instead of the configured default.",
         actions=lambda executor: [AddSubstitution("%{executor}", executor)],
+    ),
+    Parameter(
+        name="openmp_pstl_backend",
+        choices=[True, False],
+        type=bool,
+        default=False,
+        help="Enable the OpenMP compilation toolchain if the PSTL backend was set to OpenMP.",
+        actions=lambda enabled: [
+            AddCompileFlag("-fopenmp"),
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ldionne wrote:

The only thing we should have to do here is add `-fopenmp`, assuming the compiler supports OpenMP. It should not be necessary to add custom link and include flags to use this. If it is necessary to do that, I would argue the compiler should be fixed to work out of the box. Do people using `-fopenmp` also specify these paths? That would be really surprising no?

https://github.com/llvm/llvm-project/pull/66968