Inherit additional build flags from redhat-rpm-config (#1947895)
This adds additional coverage for aarch64, ppc64le, x86_64. At present, these changes have no effect: On x86_64, we used -march=x86-64-v2 as the built-in GCC default before, and on aarch64 and on ppc64le, redhat-rpm-config does not list any of the flags added here.
Resolves: #1947895