build: add `--no-warn-rwx-segments` when linking with GCC

This flag is currently not included when linking with BFD via GCC.
Without it, builds can fail when linking via GCC.

Change-Id: Id37e05f6fb4eea4620861eb1bc8668c41f21ba20
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/Makefile b/Makefile
index 8e90a75..2dc2956 100644
--- a/Makefile
+++ b/Makefile
@@ -354,6 +354,7 @@
 # LD = gcc (used when GCC LTO is enabled)
 else ifneq ($(findstring gcc,$(notdir $(LD))),)
 	# Pass ld options with Wl or Xlinker switches
+	TF_LDFLAGS		+=	$(call ld_option,-Xlinker --no-warn-rwx-segments)
 	TF_LDFLAGS		+=	-Wl,--fatal-warnings -O1
 	TF_LDFLAGS		+=	-Wl,--gc-sections