[OpenMP] Add search path for llvm-strip

[kkwli0]

Summary

Add the search path for llvm-strip instead of solely relying on the PATH environment variable setting.

Currently, make check-openmp has a few failures with the error:

/build-llvm/./bin/clang-linker-wrapper: error: Unable to find 'llvm-strip' in path

[jhuber6]

LG, thanks.

clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

if (!sys::fs::exists(StripFile)) {
     std::copy(Contents.begin(), Contents.end(), Output->getBufferStart());
     if (Error E = Output->commit())
       return std::move(E);
     StripFile = TempFile;
   }
 
   // We will use llvm-strip to remove the now unneeded section containing the
   // offloading code.
-  ErrorOr<std::string> StripPath = sys::findProgramByName("llvm-strip");
+  void *P = (void *)(intptr_t)&Help;
+  StringRef COWDir = "";
+  auto COWPath = sys::fs::getMainExecutable("llvm-strip", P);
+  if (!COWPath.empty())
+    COWDir = sys::path::parent_path(COWPath);
+  ErrorOr<std::string> StripPath =
+      sys::findProgramByName("llvm-strip", {COWDir});
   if (!StripPath)
     return createStringError(StripPath.getError(),
                              "Unable to find 'llvm-strip' in path");
 
   SmallString<128> TempFile;
   if (Error Err = createOutputFile(Prefix + "-host", Extension, TempFile))
     return std::move(Err);