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_common.mk b/lib/libc/libc_common.mk
new file mode 100644
index 0000000..fb8117f
--- /dev/null
+++ b/lib/libc/libc_common.mk
@@ -0,0 +1,43 @@
+#
+# Copyright (c) 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)	\
+