Failed benchmark due to renamed branch

[grafail]

The default branch in https://github.com/google/benchmark was renamed from "master" to "main", which breaks the cloning process during building the benchmark:
CMakeLists Original Source:

FetchContent_Declare(
    benchmark
    GIT_REPOSITORY https://github.com/google/benchmark.git
    GIT_SHALLOW TRUE
)

I created a fix for this which explicitly specifies using the main branch in #2795.