Run git from the source directory (#589) (#590)
Run git from the source directory (#589) (#590)

Git was being executed in the current directory, so could not get the
latest tag if cmake was run from a build directory. Force git to be
run from with the source directory.
google/benchmark,mockingbirdnest/benchmark,google/benchmark,mockingbirdnest/benchmark,google/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark