perf tools: Convert to GTK2_SUPPORT

For building perf without gtk+2, we can set NO_GTK2=1 as a argument of
make.  It then defines NO_GTK2_SUPPORT macro for C code to do the
proper handling.  However it usually used in a negative semantics -
e.g. #ifndef - so we saw double negations which can be misleading.
Convert it to a positive form to make it more readable.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348824728-14025-8-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 3d2181c..31a07f9 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -583,17 +583,15 @@
 	endif
 endif
 
-ifdef NO_GTK2
-	BASIC_CFLAGS += -DNO_GTK2_SUPPORT
-else
+ifndef NO_GTK2
 	FLAGS_GTK2=$(ALL_CFLAGS) $(ALL_LDFLAGS) $(EXTLIBS) $(shell pkg-config --libs --cflags gtk+-2.0 2>/dev/null)
 	ifneq ($(call try-cc,$(SOURCE_GTK2),$(FLAGS_GTK2)),y)
 		msg := $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev);
-		BASIC_CFLAGS += -DNO_GTK2_SUPPORT
 	else
 		ifeq ($(call try-cc,$(SOURCE_GTK2_INFOBAR),$(FLAGS_GTK2)),y)
 			BASIC_CFLAGS += -DHAVE_GTK_INFO_BAR
 		endif
+		BASIC_CFLAGS += -DGTK2_SUPPORT
 		BASIC_CFLAGS += $(shell pkg-config --cflags gtk+-2.0 2>/dev/null)
 		EXTLIBS += $(shell pkg-config --libs gtk+-2.0 2>/dev/null)
 		LIB_OBJS += $(OUTPUT)ui/gtk/browser.o