Revert "Reland "[benchmarks] Move libcxx's fork of google/benchmark and llvm/utils'"""

This reverts commit 1ee32055ea1dd4db70d1939cbd4f5105c2dce160.

We hit additional bot failures; in particular, Fuchsia's seems to be
related to how CMakeLists are ingested, see https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-linux-x64/b8830380874445931681/overview

GitOrigin-RevId: b2fbd45d2395f1f6ef39db72b7156724fc101e40
diff --git a/benchmarks/CMakeLists.txt b/benchmarks/CMakeLists.txt
index ac06e5a..01aab05 100644
--- a/benchmarks/CMakeLists.txt
+++ b/benchmarks/CMakeLists.txt
@@ -17,7 +17,7 @@
 ExternalProject_Add(google-benchmark
     EXCLUDE_FROM_ALL ON
     PREFIX google-benchmark
-    SOURCE_DIR ${LLVM_THIRD_PARTY_DIR}/benchmark
+    SOURCE_DIR ${LIBC_SOURCE_DIR}/../llvm/utils/benchmark
     INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}/google-benchmark
     CMAKE_CACHE_ARGS
         -DBUILD_SHARED_LIBS:BOOL=OFF