[BUG] Sanitizer CI builds are broken

[dmah42]

Describe the bug
Sanitizer builds are broken (again)

System
github actions

To reproduce
check the sanitizer actions.
for the build libc++ step we have:
/home/runner/work/benchmark/benchmark/llvm-build/include/c++/v1/__config:37:8: warning: "Libc++ only supports Clang 15 and later" [-W#warnings]

Expected behavior
it builds

[LebedevRI]

As i have warned when sanitized LLVM builds were being added...