build: remove empty $(OBJS) target

This target was added to prevent some files being deleted
by make when using chains of implicit rules.  This is no
longer required.
Signed-off-by: Mans Rullgard <mans@mansr.com>

common.mak

@@ -58,8 +58,6 @@ HOSTCFLAGS += $(IFLAGS)
 # so this saves some time on slow systems.
 .SUFFIXES:
 
-# Do not delete intermediate files from chains of implicit rules
-$(OBJS):
 endif
 
 OBJS-$(HAVE_MMX) +=  $(MMX-OBJS-yes)