[PATCH 1/1] perf build: Gracefully fail the build if BUILD_BPF_SKEL=1 is specified and clang isn't available

[arnaldo . melo]

Namhyung,

	The one you acked disabled the build and emitted a warning, but
then that was when we were trying to have BUILD_BPF_SKEL=1 as default,
this one is for the current situation, where we need to explicitely ask
for those features by explicitely adding BUILD_BPF_SKEL=1 to the make
command line, I think I can keep your Acked-by, right?

- Arnaldo

---

Build BPF skels require having a compiler able to generate BPF bytecode,
and so far this is only possible with clang, so check for its
availability and fail the build when the user explicitely ask for BPF
skels to be built.

Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>,
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxxxx>
Cc: Yang Jihong <yangjihong1@xxxxxxxxxx>,
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/Makefile.config | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 4884520f954f4b2a..70268442f7eeca50 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -216,6 +216,12 @@ ifeq ($(call get-executable,$(BISON)),)
   dummy := $(error Error: $(BISON) is missing on this system, please install it)
 endif
 
+ifeq ($(BUILD_BPF_SKEL),1)
+  ifeq ($(call get-executable,$(CLANG)),)
+    dummy := $(error $(CLANG) is missing on this system, please install it to be able to build with BUILD_BPF_SKEL=1)
+  endif
+endif
+
 ifneq ($(OUTPUT),)
   ifeq ($(shell expr $(shell $(BISON) --version | grep bison | sed -e 's/.\+ \([0-9]\+\).\([0-9]\+\).\([0-9]\+\)/\1\2\3/g') \>\= 371), 1)
     BISON_FILE_PREFIX_MAP := --file-prefix-map=$(OUTPUT)=
-- 
2.39.2