Revert "gh-actions: don't use ALWAYS_BUILD_NATIVE_TESTS build option"
Revert "gh-actions: don't use ALWAYS_BUILD_NATIVE_TESTS build option"

This reverts commit 764d010447a12d6726a72a2f417f094b6a18ba7f

I remembered why we were doing this.  We want to exercise fallbacks
on earlier ISA extensions (e.g., SSE fallbacks for AVX).

nemequ/simde,nemequ/simde,nemequ/simde