Example makefile to compile applications and bootloaders with various toolchains

Makefile

# Purpose:
#   This makefile is designed to compile applications and bootloaders with various toolchains.
#
# Features:
#   - Supports compiling applications and bootloaders separately or together.
#   - Allows specifying different compilers for applications and bootloaders within the same configuration.
#   - Supports skipping compilation for specific applications or bootloaders using the "none" keyword.
#
# Configuration Format:
#   Configurations are specified in the format:
#   app:compiler;bootloader:compiler
#   - "app" and "bootloader" represent the application and bootloader respectively.
#   - "compiler" represents the compiler/toolchain to be used for compilation.
#   - Use "none" to skip compilation for the application or bootloader.
#
# Example Configuration:
#   app1:gcc;bootloader1:iar
#   - This configuration compiles "app1" with GCC and "bootloader1" with IAR.
#
#   app2:none;bootloader2:arm-none-eabi-gcc
#   - This configuration skips compiling "app2" and compiles "bootloader2" with arm-none-eabi-gcc.

# Configurations
CONFIGURATIONS := \
    app1:gcc;bootloader1:iar \
    app2:none;bootloader2:arm-none-eabi-gcc

# Extract components from the configuration
define extract_config
    $(word 1,$(subst ;, ,$(1)))
endef

define extract_app_toolchain
    $(word 2,$(subst :, ,$(word 1,$(subst ;, ,$(1)))))
endef

define extract_bootloader_toolchain
    $(word 2,$(subst :, ,$(word 2,$(subst ;, ,$(1)))))
endef

# Set up generic targets
all: $(foreach config, $(CONFIGURATIONS), $(call build_target,$(config)))

# Target-specific variables
define build_target
    $(if $(filter none,$(call extract_config,$(1))), \
        $(info Skipping target: $(1)), \
        $(call build_target_app,$(1)) \
        $(call build_target_bootloader,$(1)))
endef

define build_target_app
    $(call build_target_impl,$(call extract_config,$(1)), \
                             $(call extract_app_toolchain,$(1)), \
                             $(call extract_config,$(1)))
endef

define build_target_bootloader
    $(call build_target_impl,$(call extract_config,$(1)), \
                             $(call extract_bootloader_toolchain,$(1)), \
                             $(call extract_config,$(1)))
endef

define build_target_impl
    $(2) -o $@_$(3) $<
endef

# Set up targets with specific compilers and configurations
$(foreach config, $(CONFIGURATIONS), \
    $(eval $(call build_target,$(config))))

.PHONY: clean

clean:
    rm -f $(addsuffix _*, $(foreach config, $(CONFIGURATIONS), $(call build_target,$(config))))