Use an ELF alias for strptime_l().

Change-Id: I21d702640cbd13839e604e49cf928fca00f3db04
diff --git a/libc/tzcode/strptime.c b/libc/tzcode/strptime.c
index ae7881e..5f91e46 100644
--- a/libc/tzcode/strptime.c
+++ b/libc/tzcode/strptime.c
@@ -97,6 +97,7 @@
 	return(_strptime(buf, fmt, tm, 1));
 }
 DEF_WEAK(strptime);
+__strong_alias(strptime_l, strptime);
 
 static char *
 _strptime(const char *buf, const char *fmt, struct tm *tm, int initialize)