String: Add __memcmpeq as build target

No bug. This commit just adds __memcmpeq as a build target so that
implementations for __memcmpeq that are not just aliases to memcmp can
be supported.

string/Makefile

@@ -34,7 +34,7 @@ routines	:= strcat strchr strcmp strcoll strcpy strcspn		\
 		   strerror _strerror strlen strnlen			\
 		   strncat strncmp strncpy				\
 		   strrchr strpbrk strsignal strspn strstr strtok	\
-		   strtok_r strxfrm memchr memcmp memmove memset	\
+		   strtok_r strxfrm memchr memcmp memcmpeq memmove memset	\
 		   mempcpy bcopy bzero ffs ffsll stpcpy stpncpy		\
 		   strcasecmp strncase strcasecmp_l strncase_l		\
 		   memccpy memcpy wordcopy strsep strcasestr		\

string/memcmpeq.c

@@ -0,0 +1,24 @@
+/* Copyright (C) 1991-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* This file is intentionally left empty.  It exists so that both
+   architectures which implement __memcmpeq seperately from memcmp and
+   architectures which implement __memcmpeq by having it alias memcmp will
+   build.
+
+   The alias for __memcmpeq to memcmp for the C implementation is in
+   memcmp.c.  */