Integrate llvm/llvm-project@6fc1deb8b749 (#21732)

Integrate LLVM at

https://github.com/llvm/llvm-project/commit/6fc1deb8b7497c36c946fa468f53d797ad54f24c
that fixes macos build.

Signed-off-by: hanhanW <hanhan0912@gmail.com>
diff --git a/third_party/llvm-project b/third_party/llvm-project
index 9a14b1d..6fc1deb 160000
--- a/third_party/llvm-project
+++ b/third_party/llvm-project
@@ -1 +1 @@
-Subproject commit 9a14b1d254a43dc0d4445c3ffa3d393bca007ba3
+Subproject commit 6fc1deb8b7497c36c946fa468f53d797ad54f24c