libbpf,selftests/bpf: Fix clean targets

Libbpf's clean target should clean out generated files in $(OUTPUT) directory
and not make assumption that $(OUTPUT) directory is current working directory.

Selftest's Makefile should delegate cleaning of libbpf-generated files to
libbpf's Makefile. This ensures more robust clean up.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200110051716.1591485-2-andriin@fb.com

tools/lib/bpf/Makefile

@@ -274,9 +274,10 @@ config-clean:
 
 clean:
 	$(call QUIET_CLEAN, libbpf) $(RM) -rf $(CMD_TARGETS)		     \
-		*.o *~ *.a *.so *.so.$(LIBBPF_MAJOR_VERSION) .*.d .*.cmd \
-		*.pc LIBBPF-CFLAGS $(BPF_HELPER_DEFS) \
-		$(SHARED_OBJDIR) $(STATIC_OBJDIR)
+		*~ .*.d .*.cmd LIBBPF-CFLAGS $(BPF_HELPER_DEFS)		     \
+		$(SHARED_OBJDIR) $(STATIC_OBJDIR)			     \
+		$(addprefix $(OUTPUT),					     \
+			    *.o *.a *.so *.so.$(LIBBPF_MAJOR_VERSION) *.pc)
 	$(call QUIET_CLEAN, core-gen) $(RM) $(OUTPUT)FEATURE-DUMP.libbpf
 
 

tools/testing/selftests/bpf/Makefile

@@ -93,6 +93,7 @@ OVERRIDE_TARGETS := 1
 override define CLEAN
 	$(call msg,    CLEAN)
 	$(RM) -r $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED) $(TEST_GEN_FILES) $(EXTRA_CLEAN)
+	$(MAKE) -C $(BPFDIR) OUTPUT=$(OUTPUT)/ clean
 endef
 
 include ../lib.mk
@@ -377,5 +378,5 @@ $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
 
 EXTRA_CLEAN := $(TEST_CUSTOM_PROGS)					\
 	prog_tests/tests.h map_tests/tests.h verifier/tests.h		\
-	feature $(OUTPUT)/*.o $(OUTPUT)/no_alu32 $(OUTPUT)/bpf_gcc	\
-	tools *.skel.h
+	feature								\
+	$(addprefix $(OUTPUT)/,*.o *.skel.h no_alu32 bpf_gcc tools)