feat(build): allow additional CFLAGS for library build

Current CFLAGS if set for library builds could impact entire build, so
allow to pass additional CFLAGs for library builds based on format
<LIBNAME>_CFLAGS.

This support is currently needed to avoid 'redundant declaration'
error from latest mbedtls-3.3, the issue is reported to mbedtls[1]
and is under consideration to remove any redundant declarations.
But till then we have to disable that compiler option while building
for mbedtls-3.3

[1]: https://github.com/Mbed-TLS/mbedtls/issues/6910

Change-Id: Ic99af22b229f8089c82110d6545f762c14a62f5c
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index a6b1d52..4815efa 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -274,10 +274,11 @@
 define MAKE_C_LIB
 $(eval OBJ := $(1)/$(patsubst %.c,%.o,$(notdir $(2))))
 $(eval DEP := $(patsubst %.o,%.d,$(OBJ)))
+$(eval LIB := $(call uppercase, $(notdir $(1))))
 
 $(OBJ): $(2) $(filter-out %.d,$(MAKEFILE_LIST)) | lib$(3)_dirs
 	$$(ECHO) "  CC      $$<"
-	$$(Q)$$(CC) $$(TF_CFLAGS) $$(CFLAGS) $(MAKE_DEP) -c $$< -o $$@
+	$$(Q)$$(CC) $$($(LIB)_CFLAGS) $$(TF_CFLAGS) $$(CFLAGS) $(MAKE_DEP) -c $$< -o $$@
 
 -include $(DEP)