build: mandate use of a build dir != src dir

build: mandate use of a build dir != src dir

Historically we've allowed builds in the main src dir, but meson does
not support this. Explicitly force separate build dir in autotools to
align with meson. We must re-enable dependency tracking which the RPM
%configure macro turns off. Without this, the build dir doesn't get
the source directory tree mirrored.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>