tools: Bump minimum LLVM C++ std to GNU++14

LLVM 9 (current release is LLVM 13) moved the minimum C++ version to
GNU++14. Bump the version numbers in the feature test and perf build.

Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20211012021321.291635-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/feature/Makefile

@@ -300,7 +300,7 @@ $(OUTPUT)test-jvmti-cmlr.bin:
 	$(BUILD)
 
 $(OUTPUT)test-llvm.bin:
-	$(BUILDXX) -std=gnu++11 				\
+	$(BUILDXX) -std=gnu++14 				\
 		-I$(shell $(LLVM_CONFIG) --includedir) 		\
 		-L$(shell $(LLVM_CONFIG) --libdir)		\
 		$(shell $(LLVM_CONFIG) --libs Core BPF)		\
@@ -308,12 +308,12 @@ $(OUTPUT)test-llvm.bin:
 		> $(@:.bin=.make.output) 2>&1
 
 $(OUTPUT)test-llvm-version.bin:
-	$(BUILDXX) -std=gnu++11 				\
+	$(BUILDXX) -std=gnu++14					\
 		-I$(shell $(LLVM_CONFIG) --includedir)		\
 		> $(@:.bin=.make.output) 2>&1
 
 $(OUTPUT)test-clang.bin:
-	$(BUILDXX) -std=gnu++11 				\
+	$(BUILDXX) -std=gnu++14					\
 		-I$(shell $(LLVM_CONFIG) --includedir) 		\
 		-L$(shell $(LLVM_CONFIG) --libdir)		\
 		-Wl,--start-group -lclangBasic -lclangDriver	\

tools/perf/Makefile.config

@@ -285,7 +285,7 @@ CORE_CFLAGS += -Wall
 CORE_CFLAGS += -Wextra
 CORE_CFLAGS += -std=gnu99
 
-CXXFLAGS += -std=gnu++11 -fno-exceptions -fno-rtti
+CXXFLAGS += -std=gnu++14 -fno-exceptions -fno-rtti
 CXXFLAGS += -Wall
 CXXFLAGS += -fno-omit-frame-pointer
 CXXFLAGS += -ggdb3