[PATCH bpf-next] selftests/bpf: Tolerate libarena skeleton failures under BPF_STRICT_BUILD=0

[HyeongJun An <sammiee5311@gmail.com>]

The Makefile documents BPF_STRICT_BUILD=0 as tolerating any BPF object,
skeleton, test object or benchmark failure so that the remaining tests
still build.  Every skeleton rule honours that through
$(if $(PERMISSIVE),...), except the three that build the libarena
skeletons.  Those invoke a sub-make with no guard, so a libarena failure
is fatal even in permissive mode.

With a libarena source that fails to compile, BPF_STRICT_BUILD=0 stops at

  make: *** [libarena/libarena.skel.h] Error 2

while an ordinary program failing the same way prints SKIP-BPF and the
build carries on.

Guard the three sub-makes the way the other skeleton rules are guarded.
The build then prints SKIP-SKEL and continues, and test_progs,
test_progs-no_alu32, test_progs-cpuv4 and bench all link.  Nothing
downstream needs a change, because the missing skeleton drops out through
the existing permissive paths and libarena.test.o is reported as
SKIP-TEST.  The default BPF_STRICT_BUILD=1 still fails on the same input.

Fixes: a6850fa388f6 ("selftests/bpf: Add BPF_STRICT_BUILD toggle")
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Assisted-by: Claude:claude-opus-5
---
 tools/testing/selftests/bpf/Makefile | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 7ea5ba1df29e..a9951774e5c8 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -835,17 +835,20 @@ LIBARENA_SKEL := libarena/libarena.skel.h
 LIBARENA_BENCH_SKEL := libarena/libarena_bench.skel.h
 
 $(LIBARENA_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
-	+$(MAKE) -C libarena libarena.skel.h $(LIBARENA_MAKE_ARGS)
+	+$(MAKE) -C libarena libarena.skel.h $(LIBARENA_MAKE_ARGS) $(if $(PERMISSIVE),|| \
+		printf '  %-12s %s\n' 'SKIP-SKEL' '$(notdir $@)' 1>&2)
 
 $(LIBARENA_BENCH_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BENCH_BPF_DEPS) | $(LIBARENA_SKEL)
-	+$(MAKE) -C libarena benchmarks $(LIBARENA_MAKE_ARGS)
+	+$(MAKE) -C libarena benchmarks $(LIBARENA_MAKE_ARGS) $(if $(PERMISSIVE),|| \
+		printf '  %-12s %s\n' 'SKIP-SKEL' '$(notdir $@)' 1>&2)
 
 ifneq ($(CLANG_HAS_ARENA_ASAN),)
 LIBARENA_ASAN_SKEL := libarena/libarena_asan.skel.h
 CFLAGS += -DHAS_BPF_ARENA_ASAN
 
 $(LIBARENA_ASAN_SKEL): $(INCLUDE_DIR)/vmlinux.h $(BPFOBJ) $(LIBARENA_BPF_DEPS)
-	+$(MAKE) -C libarena libarena_asan.skel.h $(LIBARENA_MAKE_ARGS)
+	+$(MAKE) -C libarena libarena_asan.skel.h $(LIBARENA_MAKE_ARGS) $(if $(PERMISSIVE),|| \
+		printf '  %-12s %s\n' 'SKIP-SKEL' '$(notdir $@)' 1>&2)
 endif
 
 # Define test_progs test runner.

base-commit: af0b84a9215d951d16f26b7ee34353b970cf5d4e
-- 
2.43.0