rtld: Add debug line for dlopen_object().

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

libexec/rtld-elf/rtld.c

@@ -3438,6 +3438,9 @@ dlopen_object(const char *name, int fd, Obj_Entry *refobj, int lo_flags,
     RtldLockState mlockstate;
     int result;
 
+    dbg("dlopen_object name \"%s\" fd %d refobj \"%s\" lo_flags %#x mode %#x",
+      name != NULL ? name : "<null>", fd, refobj == NULL ? "<null>" :
+      refobj->path, lo_flags, mode);
     objlist_init(&initlist);
 
     if (lockstate == NULL && !(lo_flags & RTLD_LO_EARLY)) {