BUILD: Build with make (#306)

* Use a Makefile to configure,build or clean the images.

* Update docs

* Remove old build script.

Makefile

@@ -0,0 +1,43 @@
+RELEASE_DIR = /build/release
+
+BUILDROOT=/build/buildroot
+BUILDROOT_EXTERNAL=/build/buildroot-external
+DEFCONFIG_DIR = $(BUILDROOT_EXTERNAL)/configs
+
+TARGETS := $(notdir $(patsubst %_defconfig,%,$(wildcard $(DEFCONFIG_DIR)/*_defconfig)))
+TARGETS_CONFIG := $(notdir $(patsubst %_defconfig,%-config,$(wildcard $(DEFCONFIG_DIR)/*_defconfig)))
+
+.NOTPARALLEL: $(TARGETS) $(TARGETS_CONFIG) all
+
+.PHONY: $(TARGETS) $(TARGETS_CONFIG) all clean help
+
+all: $(TARGETS)
+
+$(RELEASE_DIR):
+	mkdir -p $(RELEASE_DIR)
+
+$(TARGETS_CONFIG): %-config:
+	@echo "config $*"
+	$(MAKE) -C $(BUILDROOT) BR2_EXTERNAL=$(BUILDROOT_EXTERNAL) "$*_defconfig"
+
+$(TARGETS): %: $(RELEASE_DIR) %-config
+	@echo "build $@"
+	$(MAKE) -C $(BUILDROOT) BR2_EXTERNAL=$(BUILDROOT_EXTERNAL)
+	cp -f $(BUILDROOT)/output/images/hassos_* $(RELEASE_DIR)/
+
+	# Do not clean when building for one target
+ifneq ($(words $(filter $(TARGETS),$(MAKECMDGOALS))), 1)
+	@echo "clean $@"
+	$(MAKE) -C $(BUILDROOT) BR2_EXTERNAL=$(BUILDROOT_EXTERNAL) clean
+endif
+	@echo "finished $@"
+
+clean:
+	$(MAKE) -C $(BUILDROOT) BR2_EXTERNAL=$(BUILDROOT_EXTERNAL) clean
+
+help:
+	@echo "Supported targets: $(TARGETS)"
+	@echo "Run 'make <target>' to build a target image."
+	@echo "Run 'make all' to build all target images."
+	@echo "Run 'make clean' to clean the build output."
+	@echo "Run 'make <target>-config' to configure buildroot for a target."