[SYCL][ClangLinkerWrapper] Fix race condition (#12378)

This patch fixes a data race in the following line of the code that is
supposed to be run parallelly and needs mutex protection.

WrappedOutput.push_back(*SYCLOutputOrErr);

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

@@ -1796,6 +1796,7 @@ Expected<SmallVector<StringRef>> linkAndWrapDeviceFiles(
  // separate path inside 'linkDevice' call seen above.
  // This will eventually be refactored to use the 'common' wrapping logic
  // that is used for other offload kinds.
+ std::scoped_lock Guard(ImageMtx);
  WrappedOutput.push_back(*SYCLOutputOrErr);
  }