src: Fix checking for clang
src: Fix checking for clang

The check was trying to use the shell variable $CC instead of
the make variable $(CC); it also interpreted grep's return code
wrong: 1 means the provided pattern was *not* matched. As a
result, pdwtags was never run, not even when building with gcc.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

fabianfreyer/libvirt,libvirt/libvirt,eskultety/libvirt,jardasgit/libvirt,eskultety/libvirt,olafhering/libvirt,zippy2/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,crobinso/libvirt,eskultety/libvirt,nertpinx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,olafhering/libvirt,zippy2/libvirt,jfehlig/libvirt,nertpinx/libvirt,jardasgit/libvirt,eskultety/libvirt,jfehlig/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,olafhering/libvirt,eskultety/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt,jfehlig/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,libvirt/libvirt,olafhering/libvirt,nertpinx/libvirt,nertpinx/libvirt,libvirt/libvirt,jardasgit/libvirt,nertpinx/libvirt,andreabolognani/libvirt