[PATCH] perf build: Error for BPF skeletons without LIBBPF

[Ian Rogers <irogers@xxxxxxxxxx>]

LIBBPF requires LIBELF so doing "make BUILD_BPF_SKEL=1 NO_LIBELF=1"
fails with compiler errors about missing declarations. Similar could
happen if libbpf feature detection fails. Prefer to error when
BUILD_BPF_SKEL is enabled but LIBBPF isn't.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/Makefile.config | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index d9b699ad402c..bedb734bd6f2 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -664,6 +664,9 @@ ifdef BUILD_BPF_SKEL
   ifeq ($(feature-clang-bpf-co-re), 0)
     dummy := $(error Error: clang too old/not installed. Please install recent clang to build with BUILD_BPF_SKEL)
   endif
+  ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
+    dummy := $(error Error: BPF skeleton support requires libbpf)
+  endif
   $(call detected,CONFIG_PERF_BPF_SKEL)
   CFLAGS += -DHAVE_BPF_SKEL
 endif
-- 
2.36.1.124.g0e6072fb45-goog