Allow dropping all caps but keeping root on static binaries.

Bug: 30259228
Change-Id: I366d06c5ea1ba5def43255bf3c99fdaea16b96df
diff --git a/util.h b/util.h
index 15dd56b..78feb52 100644
--- a/util.h
+++ b/util.h
@@ -23,6 +23,9 @@
 #define warn(_msg, ...) \
 	syslog(LOG_WARNING, "libminijail: " _msg, ## __VA_ARGS__)
 
+#define pwarn(_msg, ...) \
+	warn(_msg ": %m", ## __VA_ARGS__)
+
 #define info(_msg, ...) \
 	syslog(LOG_INFO, "libminijail: " _msg, ## __VA_ARGS__)