Allow setting GOOGLETEST_PATH cmake argument. Fixes #867 (#868)
Allow setting GOOGLETEST_PATH cmake argument. Fixes #867 (#868)

In `cmake/GoogleTest.cmake`, GOOGLETEST_PATH is default-initialized, but that init forgot to
account for the fact that the patch is explicitly supposed to be user-configurable.
By passing `CACHE` to `set()` we avoid that error.
google/benchmark,google/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark,google/benchmark