perf probe: Ignore vmlinux buildid if offline kernel is given

Ignore the buildid of running kernel when both of --definition and
--vmlinux is given because that kernel should be off-line.

This also skips post-processing of kprobe event for relocating symbol
and checking blacklist, because it can not be done on off-line kernel.

E.g. without this fix perf shows an error as below
  ----
  $ perf probe --vmlinux=./vmlinux-arm --definition do_sys_open
  ./vmlinux-arm with build id 7a1f76dd56e9c4da707cd3d6333f50748141434b not found, continuing without symbols
  Failed to find symbol do_sys_open in kernel
    Error: Failed to add events.
  ----
with this fix, we can get the definition
  ----
  $ perf probe --vmlinux=./vmlinux-arm --definition do_sys_open
  p:probe/do_sys_open do_sys_open+0
  ----

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/147214228193.23638.12581984840822162131.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol-elf.c

@@ -732,7 +732,7 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
 	}
 
 	/* Always reject images with a mismatched build-id: */
-	if (dso->has_build_id) {
+	if (dso->has_build_id && !symbol_conf.ignore_vmlinux_buildid) {
 		u8 build_id[BUILD_ID_SIZE];
 
 		if (elf_read_build_id(elf, build_id, BUILD_ID_SIZE) < 0) {