fix(libc): add memcpy_s source file to libc_asm mk

Change [1] introduced the memcpy_s function and added the source file to
lib/libc/libc.mk but omitted to update lib/libc/libc_asm.mk
Arm platforms (and platforms from one partner) use OVERRIDE_LIBC=1
option as a platform default hence consume libc_asm.mk
To prevent this confusion to happen again, create libc_common.mk for the
common set of C files to build.
libc_common.mk is included by both libc.mk and libc_asm.mk
The latter adds asm implementations of libc functions.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/21450

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ibd36ea5c561e35f268048ccbefc8f47485f64bdf
diff --git a/lib/libc/libc.mk b/lib/libc/libc.mk
index 95da68c..633386c 100644
--- a/lib/libc/libc.mk
+++ b/lib/libc/libc.mk
@@ -1,42 +1,8 @@
 #
-# Copyright (c) 2016-2021, Arm Limited and Contributors. All rights reserved.
+# Copyright (c) 2016-2024, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
-
-LIBC_SRCS	:=	$(addprefix lib/libc/,		\
-			abort.c				\
-			assert.c			\
-			exit.c				\
-			memchr.c			\
-			memcmp.c			\
-			memcpy.c			\
-			memcpy_s.c			\
-			memmove.c			\
-			memrchr.c			\
-			memset.c			\
-			printf.c			\
-			putchar.c			\
-			puts.c				\
-			snprintf.c			\
-			strchr.c			\
-			strcmp.c			\
-			strlcat.c			\
-			strlcpy.c			\
-			strlen.c			\
-			strncmp.c			\
-			strnlen.c			\
-			strrchr.c			\
-			strtok.c			\
-			strtoul.c			\
-			strtoll.c			\
-			strtoull.c			\
-			strtol.c)
-
-ifeq (${ARCH},aarch64)
-LIBC_SRCS	+=	$(addprefix lib/libc/aarch64/,	\
-			setjmp.S)
-endif
+#
 
-INCLUDES	+=	-Iinclude/lib/libc		\
-			-Iinclude/lib/libc/$(ARCH)	\
+include lib/libc/libc_common.mk