mimxrt: Make linker scripts configurable.

Can simply add LD_FILE_BOARD and/or LD_FILE_COMMON
to a board's mpconfigboard.mk to change the linker
scripts, such as to change the section sizes, or
change the contents for each region. Example usage:

LD_FILE_BOARD = $(BOARD_DIR)/my_board.ld
LD_FILE_COMMON = $(BOARD_DIR)/my_common.ld

Signed-off-by: Dryw Wade <[email protected]>

Author: sfe-SparkFro

ports/mimxrt/Makefile

@@ -56,7 +56,12 @@ MCUX_SDK_DIR = lib/nxp_driver/sdk
 MCU_DIR = $(MCUX_SDK_DIR)/devices/$(MCU_SERIES)
 
 # Select linker scripts based on MCU_SERIES
-LD_FILES = boards/$(MCU_SERIES).ld boards/common.ld
+ifndef LD_FILE_COMMON
+LD_FILE_COMMON = boards/common.ld
+endif
+ifndef LD_FILE_BOARD
+LD_FILE_BOARD = boards/$(MCU_SERIES).ld
+endif
 
 # Parameter configurations for generation
 AF_FILE = boards/$(MCU_SERIES)_af.csv
@@ -544,7 +549,7 @@ endif
 #	aggregate output of preprocessor in a single linker script `link.ld`
 $(BUILD)/firmware.elf: $(OBJ)
 	$(ECHO) "PREPROCESS LINK $@"
-	$(Q)$(CC) -E -x c $(LDDEFINES) $(LD_FILES) | grep -v '^#' > $(BUILD)/link.ld
+	$(Q)$(CC) -E -x c $(LDDEFINES) $(LD_FILE_BOARD) $(LD_FILE_COMMON) | grep -v '^#' > $(BUILD)/link.ld
 	$(ECHO) "LINK $@"
 	$(Q)$(LD) -T$(BUILD)/link.ld $(LDFLAGS) -o $@ $^ $(LIBS)
 	$(Q)$(SIZE) $@
@@ -573,7 +578,7 @@ $(HEADER_BUILD)/qstrdefs.generated.h: $(BOARD_DIR)/mpconfigboard.h
 $(GEN_FLEXRAM_CONFIG_SRC): $(HEADER_BUILD)
 	$(ECHO) "Create $@"
 	$(Q)$(PYTHON) $(MAKE_FLEXRAM_LD) -d $(TOP)/$(MCU_DIR)/$(MCU_SERIES)$(MCU_CORE).h \
-		-f $(TOP)/$(MCU_DIR)/$(MCU_SERIES)$(MCU_CORE)_features.h -l boards/$(MCU_SERIES).ld -c $(MCU_SERIES) > $@
+		-f $(TOP)/$(MCU_DIR)/$(MCU_SERIES)$(MCU_CORE)_features.h -l $(LD_FILE_BOARD) -c $(MCU_SERIES) > $@
 
 # Use a pattern rule here so that make will only call make-pins.py once to make
 # both pins_gen.c and pins.h