tools: bpftool: add error message on pin failure

No error message is currently printed if the pin syscall
itself fails. It got lost in the loadall refactoring.

Fixes: 77380998 ("bpftool: add loadall command")
Reported-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/common.c

@@ -204,7 +204,11 @@ int do_pin_fd(int fd, const char *name)
 	if (err)
 		return err;
 
-	return bpf_obj_pin(fd, name);
+	err = bpf_obj_pin(fd, name);
+	if (err)
+		p_err("can't pin the object (%s): %s", name, strerror(errno));
+
+	return err;
 }
 
 int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(__u32))