cfg.mk: silence the group-qemu-caps command

A missing $(AM_V_GEN) meant the raw command was printed by
mistake.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

cfg.mk

@@ -1149,7 +1149,7 @@ test-wrap-argv:
 	$(PERL) $(top_srcdir)/tests/test-wrap-argv.pl --check $$files
 
 group-qemu-caps:
-	$(PERL) $(top_srcdir)/tests/group-qemu-caps.pl --check $(top_srcdir)/
+	$(AM_V_GEN)$(PERL) $(top_srcdir)/tests/group-qemu-caps.pl --check $(top_srcdir)/
 
 # sc_po_check can fail if generated files are not built first
 sc_po_check: \