BUG: ExtensionBuildSystem tests: Do not pass empty CMAKE_OSX_ARCHITECTURES
requested to merge github/fork/jcfr/fix-extension-build-system-tests-without-macosx-arch into master
Created by: jcfr
Since it is valid to have build without an architecture explicitly set (meaning no -arch x86_64 compiler flag), this commit do not force an empty value in the CMakeCache.
Reported by: Nicole Aucoin nicole@bwh.harvard.edu