[libc] Fixing the build command for benchmarks.

Building libc without clang fails with:
CMake Error at /home/asteinhauser/llvm-project/libc/CMakeLists.txt:49 (message):
'clang' and 'clang-tools-extra' are required in LLVM_ENABLE_PROJECTS to
lint llvm-libc. The linting step performs important checks to help prevent
the introduction of subtle bugs, but it may increase build times.

Reviewers: sivachandra

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D80495

GitOrigin-RevId: 504d8d9d8a20fae1717bcf65dbc7577d0f26ffd7
diff --git a/utils/benchmarks/README.md b/utils/benchmarks/README.md
index fdd0223..ed7d80e 100644
--- a/utils/benchmarks/README.md
+++ b/utils/benchmarks/README.md
@@ -35,7 +35,7 @@
 
 ```shell
 cd llvm-project
-cmake -B/tmp/build -Sllvm -DLLVM_ENABLE_PROJECTS=libc -DCMAKE_BUILD_TYPE=Release
+cmake -B/tmp/build -Sllvm -DLLVM_ENABLE_PROJECTS='clang;clang-tools-extra;libc' -DCMAKE_BUILD_TYPE=Release
 make -C /tmp/build -j display-libc-memcpy-benchmark-small
 ```