[libcxx] [libcxxabi] [libunwind] [libc++] Build Google Benchmark directly from Lit (PR #160367)

[Louis Dionne via cfe-commits]

ldionne wrote:

I am going to abandon this in favour of building GoogleBenchmark once during the configuration of the test suite. This will address the problem of rebuilding GoogleBenchmark for every benchmark.

https://github.com/llvm/llvm-project/pull/160367