Fix clang build by making herror consistently weak.

* clang, unlike GCC, does not allow a weak declaration to override
  a strong definition. We need to make herror's definition in
  addition to declaring the weak alias above.

Change-Id: Iac1c00e66bdd73d6e214e2302e18a0d51b18c9d6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8148
Reviewed-by: Fredrik Holmqvist <[email protected]>

src/system/libnetwork/netresolv/resolv/herror.c

@@ -89,6 +89,7 @@ __weak_alias(herror,_herror)
  * herror --
  *	print the error indicated by the h_errno value.
  */
+__attribute__((weak))
 void
 herror(const char *s) {
 	struct iovec iov[4], *v = iov;