perf build: Force llvm/clang test compile output to .make.output

So we can see the output of feature compile in following files:

  tools/build/feature/test-llvm.make.output
  tools/build/feature/test-llvm-version.make.output
  tools/build/feature/test-clang.make.output
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180307155020.32613-20-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/feature/Makefile

@@ -260,11 +260,13 @@ $(OUTPUT)test-llvm.bin:
 		-I$(shell $(LLVM_CONFIG) --includedir) 		\
 		-L$(shell $(LLVM_CONFIG) --libdir)		\
 		$(shell $(LLVM_CONFIG) --libs Core BPF)		\
-		$(shell $(LLVM_CONFIG) --system-libs)
+		$(shell $(LLVM_CONFIG) --system-libs)		\
+		> $(@:.bin=.make.output) 2>&1
 
 $(OUTPUT)test-llvm-version.bin:
 	$(BUILDXX) -std=gnu++11 				\
-		-I$(shell $(LLVM_CONFIG) --includedir)
+		-I$(shell $(LLVM_CONFIG) --includedir)		\
+		> $(@:.bin=.make.output) 2>&1
 
 $(OUTPUT)test-clang.bin:
 	$(BUILDXX) -std=gnu++11 				\
@@ -274,7 +276,8 @@ $(OUTPUT)test-clang.bin:
 		  -lclangFrontend -lclangEdit -lclangLex	\
 		  -lclangAST -Wl,--end-group 			\
 		$(shell $(LLVM_CONFIG) --libs Core option)	\
-		$(shell $(LLVM_CONFIG) --system-libs)
+		$(shell $(LLVM_CONFIG) --system-libs)		\
+		> $(@:.bin=.make.output) 2>&1
 
 -include $(OUTPUT)*.d