tools/perf/build: Split out feature check: 'libelf'

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-qznhihaasbysfqO7ffvRsf9q@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

tools/perf/config/Makefile

@@ -108,6 +108,7 @@ FEATURE_TESTS =				\
 	volatile-register-var		\
 	fortify-source			\
 	bionic				\
+	libelf				\
 	libnuma
 
 $(foreach test,$(FEATURE_TESTS),$(call feature_check,$(test),$(test)))
@@ -164,8 +165,7 @@ ifdef NO_LIBELF
   NO_DEMANGLE := 1
   NO_LIBUNWIND := 1
 else
-  FLAGS_LIBELF=$(CFLAGS) $(LDFLAGS) $(EXTLIBS)
-  ifneq ($(call try-cc,$(SOURCE_LIBELF),$(FLAGS_LIBELF),libelf),y)
+  ifeq ($(feature-libelf), 0)
     FLAGS_GLIBC=$(CFLAGS) $(LDFLAGS)
     ifeq ($(call try-cc,$(SOURCE_GLIBC),$(FLAGS_GLIBC),glibc),y)
       LIBC_SUPPORT := 1

tools/perf/config/feature-checks/Makefile

@@ -6,6 +6,7 @@ FILES=					\
 	test-volatile-register-var	\
 	test-fortify-source		\
 	test-bionic			\
+	test-libelf			\
 	test-libnuma
 
 CC := $(CC) -MD
@@ -34,6 +35,9 @@ test-fortify-source:
 test-bionic:
 	$(BUILD)
 
+test-libelf:
+	$(BUILD) -lelf
+
 test-libnuma:
 	$(BUILD) -lnuma
 

tools/perf/config/feature-checks/test-libelf.c

+#include <libelf.h>
+
+int main(void)
+{
+	Elf *elf = elf_begin(0, ELF_C_READ, 0);
+	return (long)elf;
+}