meson: prepare move of QEMU_CFLAGS to meson

Clean up the handling of compiler flags in meson.build, splitting
the general flags that should be included in subprojects as well,
from warning flags that only apply to QEMU itself.  The two were
mixed in both configure tests and meson tests.

This split makes it easier to move the compiler tests piecewise
from configure to Meson.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed