fix(build): allow gcc linker on Aarch32 platforms

When trying to compile and link with gcc on an Aarch32 platform, there
is the following error:
arm-none-eabi-gcc: error: unrecognized command-line option
 '-mno-fix-cortex-a53-843419'; did you mean '-mno-fix-cortex-m3-ldrd'?

This option seems specific to Aarch64 version of GCC.
Enclose it with a check on ARCH=aarch64.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I8c8cb784ce2f2938c4c6999745dda09ee9a5669d
diff --git a/Makefile b/Makefile
index 907ae21..6a2eeca 100644
--- a/Makefile
+++ b/Makefile
@@ -370,8 +370,10 @@
 
 # GCC automatically adds fix-cortex-a53-843419 flag when used to link
 # which breaks some builds, so disable if errata fix is not explicitly enabled
-	ifneq (${ERRATA_A53_843419},1)
-		TF_LDFLAGS	+= 	-mno-fix-cortex-a53-843419
+	ifeq (${ARCH},aarch64)
+		ifneq (${ERRATA_A53_843419},1)
+			TF_LDFLAGS	+= 	-mno-fix-cortex-a53-843419
+		endif
 	endif
 	TF_LDFLAGS		+= 	-nostdlib
 	TF_LDFLAGS		+=	$(subst --,-Xlinker --,$(TF_LDFLAGS_$(ARCH)))