perf tools: Check for flex and bison before continuing building

Check whether both executables are present on the system before
continuing with the build instead of failing halfway, if either are
missing.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1359979554-9160-1-git-send-email-bp@alien8.deSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile

@@ -149,6 +149,8 @@ RM = rm -f
 MKDIR = mkdir
 FIND = find
 INSTALL = install
+FLEX = flex
+BISON= bison
 
 # sparse is architecture-neutral, which means that we need to tell it
 # explicitly what architecture to check for. Fix this up for yours..
@@ -158,6 +160,14 @@ ifneq ($(MAKECMDGOALS),clean)
 ifneq ($(MAKECMDGOALS),tags)
 -include config/feature-tests.mak
 
+ifeq ($(call get-executable,$(FLEX)),)
+	dummy := $(error Error: $(FLEX) is missing on this system, please install it)
+endif
+
+ifeq ($(call get-executable,$(BISON)),)
+	dummy := $(error Error: $(BISON) is missing on this system, please install it)
+endif
+
 ifeq ($(call try-cc,$(SOURCE_HELLO),$(CFLAGS) -Werror -fstack-protector-all,-fstack-protector-all),y)
 	CFLAGS := $(CFLAGS) -fstack-protector-all
 endif
@@ -282,9 +292,6 @@ endif
 
 export PERL_PATH
 
-FLEX = flex
-BISON= bison
-
 $(OUTPUT)util/parse-events-flex.c: util/parse-events.l $(OUTPUT)util/parse-events-bison.c
 	$(QUIET_FLEX)$(FLEX) --header-file=$(OUTPUT)util/parse-events-flex.h $(PARSER_DEBUG_FLEX) -t util/parse-events.l > $(OUTPUT)util/parse-events-flex.c