depends: Add 'make clean' and 'make clean-all' rules

It's useful to have a standard way to clean up the work done by the
depends system when testing changes to it.

The `make clean-all` rule removes build artifacts for all
supported architectures (in addition to sources/), while `make clean`
only removes artifacts for current architecture (`BUILD`).

Author: hkjn

depends/Makefile

@@ -1,6 +1,7 @@
 .NOTPARALLEL :
 
 SOURCES_PATH ?= $(BASEDIR)/sources
+WORK_PATH = $(BASEDIR)/work
 BASE_CACHE ?= $(BASEDIR)/built
 SDK_PATH ?= $(BASEDIR)/SDKs
 NO_QT ?=
@@ -29,9 +30,9 @@ else
 release_type=release
 endif
 
-base_build_dir=$(BASEDIR)/work/build
-base_staging_dir=$(BASEDIR)/work/staging
-base_download_dir=$(BASEDIR)/work/download
+base_build_dir=$(WORK_PATH)/build
+base_staging_dir=$(WORK_PATH)/staging
+base_download_dir=$(WORK_PATH)/download
 canonical_host:=$(shell ./config.sub $(HOST))
 build:=$(shell ./config.sub $(BUILD))
 
@@ -165,6 +166,12 @@ $(host_prefix)/share/config.site: check-packages
 
 check-packages: check-sources
 
+clean-all: clean
+	@rm -rf $(SOURCES_PATH) x86_64* i686* mips* arm* aarch64*
+
+clean:
+	@rm -rf $(WORK_PATH) $(BASE_CACHE) $(BUILD)
+
 install: check-packages $(host_prefix)/share/config.site
 
 
@@ -178,4 +185,4 @@ download-win:
 	@$(MAKE) -s HOST=x86_64-w64-mingw32 download-one
 download: download-osx download-linux download-win
 
-.PHONY: install cached download-one download-osx download-linux download-win download check-packages check-sources
+.PHONY: install cached clean clean-all download-one download-osx download-linux download-win download check-packages check-sources