Build: support per-BL LDFLAGS

make_helpers/build_macros.mk supports per-BL CFLAGS. For example,
you can pass compiler flags only to BL31 by using BL31_CFLAGS.

This commit adds per-BL LDFLAGS support, which is useful as well.

My main motivation of this addition is to use it for ENABLE_PIE.
When ENABLE_PIE is enabled, some linker flags are added to TF_LDFLAGS,
which affects all the TF images. It will make more sense to pass the
relevant options only to BL images that support it.

Change-Id: I203acaab0091db5ae0ea6e66460ee7dc8d9c4d75
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

make_helpers/build_macros.mk

@@ -412,6 +412,7 @@ bl${1}_dirs: | ${OBJ_DIRS}
 
 $(eval $(call MAKE_OBJS,$(BUILD_DIR),$(SOURCES),$(1)))
 $(eval $(call MAKE_LD,$(LINKERFILE),$(BL_LINKERFILE),$(1)))
+$(eval BL_LDFLAGS := $(BL$(call uppercase,$(1))_LDFLAGS))
 
 ifeq ($(USE_ROMLIB),1)
 $(ELF): romlib.bin
@@ -427,7 +428,7 @@ else
 		$$(CC) $$(TF_CFLAGS) $$(CFLAGS) -xc -c - -o $(BUILD_DIR)/build_message.o
 endif
 ifneq ($(findstring armlink,$(notdir $(LD))),)
-	$$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) --entry=bl${1}_entrypoint \
+	$$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) $(BL_LDFLAGS) --entry=bl${1}_entrypoint \
 		--predefine="-D__LINKER__=$(__LINKER__)" \
 		--predefine="-DTF_CFLAGS=$(TF_CFLAGS)" \
 		--map --list="$(MAPFILE)" --scatter=${PLAT_DIR}/scat/bl${1}.scat \
@@ -438,7 +439,7 @@ else ifneq ($(findstring gcc,$(notdir $(LD))),)
 		-Wl,-T$(LINKERFILE) $(BUILD_DIR)/build_message.o \
 		$(OBJS) $(LDPATHS) $(LIBWRAPPER) $(LDLIBS) $(BL_LIBS)
 else
-	$$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) -Map=$(MAPFILE) \
+	$$(Q)$$(LD) -o $$@ $$(TF_LDFLAGS) $$(LDFLAGS) $(BL_LDFLAGS) -Map=$(MAPFILE) \
 		--script $(LINKERFILE) $(BUILD_DIR)/build_message.o \
 		$(OBJS) $(LDPATHS) $(LIBWRAPPER) $(LDLIBS) $(BL_LIBS)
 endif