Summary: minor, check certain compiler flags regardless of CC flavour

Summary: minor, check certain compiler flags regardless of CC flavour
Keywords: bldchn

This changeset, in preparation to upcoming clang support, checks for
certain compiler flags (warnings at the moment) regardless of flavour.
It seems many compilers actually support a lot more gcc flags than gcc
itself, so check for them without checking for the flavour first.

This might break Sun studio build but Sun isn't shining anymore, is it?

* m4/sxe-compiler.m4: check for warning flags irrespective of CC flavour

Signed-off-by: Sebastian Freundt <hroptatyr@fresse.org>