depends: teach 'make download' to download sources for all hosts

depends/Makefile

@@ -122,5 +122,12 @@ $(host_prefix)/share/config.site : config.site.in $(host_prefix)/.stamp_$(final_
 	$(AT)touch $@
 
 install: $(host_prefix)/share/config.site
-download: $(all_sources)
-.PHONY: install cached
+download-one: $(all_sources)
+download-osx:
+	@$(MAKE) -s HOST=x86_64-apple-darwin11 download-one
+download-linux:
+	@$(MAKE) -s HOST=x86_64-unknown-linux-gnu download-one
+download-win:
+	@$(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

depends/README.usage

@@ -29,4 +29,7 @@ If some packages are not built, for example 'make NO_WALLET=1', the appropriate
 options will be passed to bitcoin's configure. In this case, --disable-wallet.
 
 Additional targets:
-download: run 'make download' to fetch sources without building them
+download: run 'make download' to fetch all sources without building them
+download-osx: run 'make download-osx' to fetch all sources needed for osx builds
+download-win: run 'make download-win' to fetch all sources needed for win builds
+download-linux: run 'make download-linux' to fetch all sources needed for linux builds