build: use GCC to link by default

When configuring GNU GCC as the C compiler, we usually use the GNU BFD
linker directly to link by default. However, this complicates things
because we also need to support LTO, which can only be done when linking
is done via the C compiler, and we cannot change the linker later on if
some other part of the build system wants to enable LTO.

This change migrates the default choice of linker to GCC if the C
compiler is GCC, in order to enable this use-case. This should have no
impact on anything outside of the build system, as by default GCC merely
acts as a wrapper around BFD.

Change-Id: I40771be2b0571def67bbfde9e877e7629ec8cdaa
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/lib/romlib/Makefile b/lib/romlib/Makefile
index f11e577..62cbf3e 100644
--- a/lib/romlib/Makefile
+++ b/lib/romlib/Makefile
@@ -30,9 +30,10 @@
   Q :=
 endif
 
-LDFLAGS := --gc-sections -O1
+LDFLAGS := -Wl,--gc-sections -nostdlib
+
 ifeq ($(DEBUG),1)
-   LDFLAGS += -Map=$(MAPFILE)
+   LDFLAGS += -Wl,-Map=$(MAPFILE)
 endif
 
 ifeq (${ARM_ARCH_MINOR},0)
diff --git a/make_helpers/toolchain.mk b/make_helpers/toolchain.mk
index 7255509..5c77782 100644
--- a/make_helpers/toolchain.mk
+++ b/make_helpers/toolchain.mk
@@ -287,7 +287,7 @@
 
 guess-gnu-gcc-cpp = $(1) # Use the C compiler
 guess-gnu-gcc-as = $(1) # Use the C compiler
-guess-gnu-gcc-ld = $(if $(filter 1,$(ENABLE_LTO)),$(1),$(shell $(1) --print-prog-name ld.bfd 2>$(nul)))
+guess-gnu-gcc-ld = $(1) # Use the C compiler
 guess-gnu-gcc-oc = $(shell $(1) --print-prog-name objcopy 2>$(nul))
 guess-gnu-gcc-od = $(shell $(1) --print-prog-name objdump 2>$(nul))
 guess-gnu-gcc-ar = $(patsubst %$(notdir $(1)),%$(subst gcc,gcc-ar,$(notdir $(1))),$(1))
diff --git a/make_helpers/toolchains/aarch32.mk b/make_helpers/toolchains/aarch32.mk
index 226bc75..3475c91 100644
--- a/make_helpers/toolchains/aarch32.mk
+++ b/make_helpers/toolchains/aarch32.mk
@@ -7,7 +7,7 @@
 aarch32-cc-default := $(or $(CROSS_COMPILE),arm-none-eabi-)gcc
 aarch32-cpp-default := $(or $(CROSS_COMPILE),arm-none-eabi-)gcc
 aarch32-as-default := $(or $(CROSS_COMPILE),arm-none-eabi-)gcc
-aarch32-ld-default := $(or $(CROSS_COMPILE),arm-none-eabi-)ld.bfd
+aarch32-ld-default := $(or $(CROSS_COMPILE),arm-none-eabi-)gcc
 aarch32-oc-default := $(or $(CROSS_COMPILE),arm-none-eabi-)objcopy
 aarch32-od-default := $(or $(CROSS_COMPILE),arm-none-eabi-)objdump
 aarch32-ar-default := $(or $(CROSS_COMPILE),arm-none-eabi-)gcc-ar
diff --git a/make_helpers/toolchains/aarch64.mk b/make_helpers/toolchains/aarch64.mk
index 15c5757..d83d918 100644
--- a/make_helpers/toolchains/aarch64.mk
+++ b/make_helpers/toolchains/aarch64.mk
@@ -7,7 +7,7 @@
 aarch64-cc-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)gcc
 aarch64-cpp-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)gcc
 aarch64-as-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)gcc
-aarch64-ld-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)ld.bfd
+aarch64-ld-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)gcc
 aarch64-oc-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)objcopy
 aarch64-od-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)objdump
 aarch64-ar-default := $(or $(CROSS_COMPILE),aarch64-none-elf-)gcc-ar
diff --git a/make_helpers/toolchains/rk3399-m0.mk b/make_helpers/toolchains/rk3399-m0.mk
index c61b6e8..f57d658 100644
--- a/make_helpers/toolchains/rk3399-m0.mk
+++ b/make_helpers/toolchains/rk3399-m0.mk
@@ -7,7 +7,7 @@
 rk3399-m0-cc-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)gcc
 rk3399-m0-cpp-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)gcc
 rk3399-m0-as-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)gcc
-rk3399-m0-ld-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)ld.bfd
+rk3399-m0-ld-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)gcc
 rk3399-m0-oc-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)objcopy
 rk3399-m0-od-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)objdump
 rk3399-m0-ar-default := $(or $(M0_CROSS_COMPILE),arm-none-eabi-)gcc-ar
diff --git a/tools/renesas/rcar_layout_create/makefile b/tools/renesas/rcar_layout_create/makefile
index baa6e7e..919c1de 100644
--- a/tools/renesas/rcar_layout_create/makefile
+++ b/tools/renesas/rcar_layout_create/makefile
@@ -89,19 +89,19 @@
 # Linker
 ###################################################
 $(OUTPUT_FILE_SA0) : $(MEMORY_DEF_SA0) $(OBJ_FILE_SA0)
-	$(aarch64-ld) $(OBJ_FILE_SA0)		 	\
+	$(aarch64-ld) $(OBJ_FILE_SA0) -nostdlib	\
 	-T $(MEMORY_DEF_SA0)			\
 	-o $(OUTPUT_FILE_SA0)			\
-	-Map $(FILE_NAME_SA0).map 		\
+	-Wl,-Map $(FILE_NAME_SA0).map 		\
 
 	$(aarch64-oc) -O srec --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA0) $(FILE_NAME_SA0).srec
 	$(aarch64-oc) -O binary --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA0) $(FILE_NAME_SA0).bin
 
 $(OUTPUT_FILE_SA6) : $(MEMORY_DEF_SA6) $(OBJ_FILE_SA6)
-	$(aarch64-ld) $(OBJ_FILE_SA6)		 	\
+	$(aarch64-ld) $(OBJ_FILE_SA6) -nostdlib	\
 	-T $(MEMORY_DEF_SA6)			\
 	-o $(OUTPUT_FILE_SA6)			\
-	-Map $(FILE_NAME_SA6).map 		\
+	-Wl,-Map $(FILE_NAME_SA6).map 		\
 
 	$(aarch64-oc) -O srec --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA6) $(FILE_NAME_SA6).srec
 	$(aarch64-oc) -O binary --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA6) $(FILE_NAME_SA6).bin
diff --git a/tools/renesas/rzg_layout_create/makefile b/tools/renesas/rzg_layout_create/makefile
index 4cab5fb..e1c242d 100644
--- a/tools/renesas/rzg_layout_create/makefile
+++ b/tools/renesas/rzg_layout_create/makefile
@@ -86,19 +86,19 @@
 # Linker
 ###################################################
 $(OUTPUT_FILE_SA0) : $(MEMORY_DEF_SA0) $(OBJ_FILE_SA0)
-	$(aarch64-ld) $(OBJ_FILE_SA0)		 	\
+	$(aarch64-ld) $(OBJ_FILE_SA0) -nostdlib	\
 	-T $(MEMORY_DEF_SA0)			\
 	-o $(OUTPUT_FILE_SA0)			\
-	-Map $(FILE_NAME_SA0).map 		\
+	-Wl,-Map $(FILE_NAME_SA0).map 		\
 
 	$(aarch64-oc) -O srec --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA0) $(FILE_NAME_SA0).srec
 	$(aarch64-oc) -O binary --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA0) $(FILE_NAME_SA0).bin
 
 $(OUTPUT_FILE_SA6) : $(MEMORY_DEF_SA6) $(OBJ_FILE_SA6)
-	$(aarch64-ld) $(OBJ_FILE_SA6)		 	\
+	$(aarch64-ld) $(OBJ_FILE_SA6) -nostdlib	\
 	-T $(MEMORY_DEF_SA6)			\
 	-o $(OUTPUT_FILE_SA6)			\
-	-Map $(FILE_NAME_SA6).map 		\
+	-Wl,-Map $(FILE_NAME_SA6).map 		\
 
 	$(aarch64-oc) -O srec --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA6) $(FILE_NAME_SA6).srec
 	$(aarch64-oc) -O binary --adjust-vma=$(RCAR_VMA_ADJUST_ADDR) --srec-forceS3  $(OUTPUT_FILE_SA6) $(FILE_NAME_SA6).bin