[pstl] Initial implementation of OpenMP backend, on behalf of Christopher Nelson nadiasvertex@gmail.com

Phabricator Review:
https://reviews.llvm.org/D99836

A couple of parallel patterns still remains serial - "Parallel partial sort", and "Parallel transform scan" - there are //TODOs in the code.

GitOrigin-RevId: 6069a6a5049497a32a50a49661c2f4169078bdba
diff --git a/cmake/Modules/DefineLinkerScript.cmake b/cmake/Modules/DefineLinkerScript.cmake
index be7f026..71a4308 100644
--- a/cmake/Modules/DefineLinkerScript.cmake
+++ b/cmake/Modules/DefineLinkerScript.cmake
@@ -31,7 +31,7 @@
   set(link_libraries)
   if (interface_libs)
     foreach(lib IN LISTS interface_libs)
-      if ("${lib}" STREQUAL "cxx-headers")
+      if ("${lib}" MATCHES "cxx-headers|ParallelSTL")
         continue()
       endif()
       # If ${lib} is not a target, we use a dummy target which we know will