Better Makefile target detection (#8223)

Replace regex-based target detection for Makefiles with a preliminary "make -q"
to check if a target exists. This does not work for NetBSD make; additional work
is required to detect if NetBSD make is present and to use a regex in that case.
The affected makefile target checks are only performed when the "--test" flag is
added to a "spack install" invocation.