build: removed recursive make

generate targets separately, avoiding the need to recursively call
make

This also fixes disabling quiet, like this:

  make FOXEER_F421 QUIET=

also see "Recursive Make Considered Harmful" paper by Peter Miller

Makefile

@@ -50,17 +50,14 @@ FIRMWARE_VERSION := $(VERSION_MAJOR).$(VERSION_MINOR)
 CFLAGS_BASE := -DUSE_MAKE -fsingle-precision-constant -fomit-frame-pointer -ffast-math
 CFLAGS_BASE += -I$(MAIN_INC_DIR) -g3 -O3 -Wall -ffunction-sections
 
-CFLAGS_COMMON := $(CFLAGS_BASE) -D$(TARGET)
+CFLAGS_COMMON := $(CFLAGS_BASE)
 
 # Linker options
 LDFLAGS_COMMON := -specs=nano.specs $(LIBS) -Wl,--gc-sections -Wl,--print-memory-usage
 
 # Search source files
 SRC_COMMON := $(foreach dir,$(SRC_DIRS_COMMON),$(wildcard $(dir)/*.[cs]))
 
-TARGET_FNAME = $(IDENTIFIER)_$(TARGET)_$(FIRMWARE_VERSION)
-TARGET_BASENAME = $(BIN_DIR)/$(TARGET_FNAME)
-
 # configure some directories that are relative to wherever ROOT_DIR is located
 OBJ := obj
 BIN_DIR := $(ROOT)/$(OBJ)
@@ -79,45 +76,37 @@ clean :
 	@echo Removing $(OBJ) directory
 	@$(RM) -rf $(OBJ)
 
+#####################
+# main firmware build
+define CREATE_BUILD_TARGET
+$(2)_BASENAME = $(BIN_DIR)/$(IDENTIFIER)_$(2)_$(FIRMWARE_VERSION)
+
+$(2) : $$($(2)_BASENAME).bin
+
+# Generate bin and hex files from elf
+$$($(2)_BASENAME).bin: $$($(2)_BASENAME).elf
+	echo building BIN $$@
+	@$(ECHO) Generating $$(notdir $$@)
+	$(QUIET)$(OBJCOPY) -O binary $$(<) $$@
+	$(QUIET)$(OBJCOPY) $$(<) -O ihex $$(@:.bin=.hex)
 
-binary : $(TARGET_BASENAME).bin
+CFLAGS_$(2) = $(MCU_$(1)) -D$(2) $(CFLAGS_$(1)) $(CFLAGS_COMMON)
+LDFLAGS_$(2) = $(LDFLAGS_COMMON) $(LDFLAGS_$(1)) -T$(LDSCRIPT_$(1))
+
+$$($(2)_BASENAME).elf: $(SRC_COMMON) $$(SRC_$(1))
+	@$(ECHO) Compiling $$(notdir $$@)
+	$(QUIET)$(MKDIR) -p $(OBJ)
+	$(QUIET)$(CC) $$(CFLAGS_$(2)) $$(LDFLAGS_$(2)) -MMD -MP -MF $$(@:.elf=.d) -o $$(@) $(SRC_COMMON) $$(SRC_$(1))
 # we copy debug.elf to give us a constant debug target for vscode
 # this means the debug button will always debug the last target built
-	@$(CP) -f $(OBJ)$(DSEP)$(TARGET_FNAME).elf $(OBJ)$(DSEP)debug.elf > $(NUL)
+	@$(CP) -f $$(@) $(OBJ)$(DSEP)debug.elf > $(NUL)
 # also copy the openocd.cfg from the MCU directory to obj/openocd.cfg for auto config of Cortex-Debug
 # in vscode
-	@$(CP) -f Mcu$(DSEP)$(call lc,$(MCU_TYPE))$(DSEP)openocd.cfg $(OBJ)$(DSEP)openocd.cfg > $(NUL)
-	@$(ECHO) done $(TARGET)
-
-# create targets compiling each MCU types targets
-define CREATE_MCU_TARGETS
-$$(TARGETS_$(1)) :
-	@$$(MAKE) -s MCU_TYPE=$(1) TARGET=$$@ binary
-endef
-$(foreach MCU,$(MCU_TYPES),$(eval $(call CREATE_MCU_TARGETS,$(MCU))))
-
-
-# Compile target
-$(TARGET_BASENAME).elf: CFLAGS := $(MCU_$(MCU_TYPE)) $(CFLAGS_$(MCU_TYPE)) $(CFLAGS_COMMON)
-$(TARGET_BASENAME).elf: LDFLAGS := $(LDFLAGS_COMMON) $(LDFLAGS_$(MCU_TYPE)) -T$(LDSCRIPT_$(MCU_TYPE))
-$(TARGET_BASENAME).elf: $(SRC_COMMON) $(SRC_$(MCU_TYPE))
-	@$(ECHO) Compiling $(notdir $@)
-	$(QUIRT)$(MKDIR) -p $(OBJ)
-	$(QUIET)$(CC) $(CFLAGS) $(LDFLAGS) -MMD -MP -MF $(@:.elf=.d) -o $(@) $(SRC_COMMON) $(SRC_$(MCU_TYPE))
-
-# Generate bin and hex files
-$(TARGET_BASENAME).bin: $(TARGET_BASENAME).elf
-	@$(ECHO) Generating $(notdir $@)
-	$(QUIET)$(OBJCOPY) -O binary $(<) $@
-	$(QUIET)$(OBJCOPY) $(<) -O ihex $(@:.bin=.hex)
-
-# include the targets for installing tools
-include $(ROOT)/make/tools_install.mk
-
-define SHOW_MCU_TARGETS
-$(1) Targets $(TARGETS_$(1))\n
+	@$(CP) -f Mcu$(DSEP)$(call lc,$(1))$(DSEP)openocd.cfg $(OBJ)$(DSEP)openocd.cfg > $(NUL)
 endef
+$(foreach MCU,$(MCU_TYPES),$(foreach TARGET,$(TARGETS_$(MCU)), $(eval $(call CREATE_BUILD_TARGET,$(MCU),$(TARGET)))))
 
+##################
 # bootloader build
 BOOTLOADER_VERSION := $(shell $(FGREP) "define BOOTLOADER_VERSION" $(MAIN_INC_DIR)/version.h | $(CUT) -d" " -f3 )
 
@@ -163,6 +152,9 @@ ALL_BOOTLOADERS := $(foreach MCU,$(BL_MCU_TYPES),$(foreach PIN,$(BOOTLOADER_PINS
 
 bootloaders: $(ALL_BOOTLOADERS)
 
+# include the targets for installing tools
+include $(ROOT)/make/tools_install.mk
+
 # useful target to list all of the board targets so you can see what
 # make target to use for your board
 targets: