arm, powerpc: Update cc-version tests to check for cc-name as well

arm, powerpc: Update cc-version tests to check for cc-name as well

For compatibility clang will report some gcc version.  However since we
are checking gcc versions in order to then fail to build, we should
limit these tests only to when we are using gcc and not clang.

Signed-off-by: Tom Rini <trini@konsulko.com>