Merge branch 'bpftool: improve error handing for missing .BTF section'

Changbin Du says:

====================
Display error message for missing ".BTF" section and clean up empty
vmlinux.h file.

v3:
 - fix typo and make error message consistent. (Andrii Nakryiko)
 - split out perf change.
v2:
 - remove vmlinux specific error info.
 - use builtin target .DELETE_ON_ERROR: to delete empty vmlinux.h
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

tools/bpf/bpftool/Makefile

@@ -289,3 +289,6 @@ FORCE:
 .PHONY: all FORCE bootstrap clean install-bin install uninstall
 .PHONY: doc doc-clean doc-install doc-uninstall
 .DEFAULT_GOAL := all
+
+# Delete partially updated (corrupted) files on error
+.DELETE_ON_ERROR:

tools/lib/bpf/btf.c

@@ -1003,6 +1003,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 	err = 0;
 
 	if (!btf_data) {
+		pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path);
 		err = -ENOENT;
 		goto done;
 	}

tools/testing/selftests/bpf/Makefile

@@ -626,3 +626,6 @@ EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)	\
 			       liburandom_read.so)
 
 .PHONY: docs docs-clean
+
+# Delete partially updated (corrupted) files on error
+.DELETE_ON_ERROR: