Makefile cosmetics

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@20422 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

Makefile

@@ -35,7 +35,7 @@ FF_DEP_LIBS  := $(DEP_LIBS)
 
 ALL_TARGETS-$(BUILD_DOC)    += documentation
 
-ifneq ($(PROGS),)
+ifdef PROGS
 INSTALL_TARGETS-yes             += install-progs install-data
 INSTALL_TARGETS-$(BUILD_DOC)    += install-man
 endif