enable _longjmp alias else less fails to build

libc/sysdeps/linux/common/longjmp.c

@@ -47,4 +47,4 @@ void __libc_longjmp (sigjmp_buf env, int val)
 strong_alias(__libc_longjmp,longjmp)
 strong_alias(__libc_longjmp,siglongjmp)
 strong_alias(__libc_longjmp,__libc_siglongjmp)
-/* weak_alias (__libc_longjmp, _longjmp) */
+weak_alias (__libc_longjmp, _longjmp)