gui: new command to launch the https://github.com/rclone/rclone-web/ GUI

This adds a new gui command which runs an embedded copy of the GUI at

https://github.com/rclone/rclone-web/

The GUI release is fetched as part of the CI build.

Makefile

@@ -45,9 +45,9 @@ LINTTAGS=--build-tags "$(GOTAGS)"
 endif
 LDFLAGS=--ldflags "-s -X github.com/rclone/rclone/fs.Version=$(TAG)"
 
-.PHONY: rclone test_all vars version
+.PHONY: rclone test_all vars version fetch-gui
 
-rclone:
+rclone: fetch-gui
 ifeq ($(GO_OS),windows)
 	go run bin/resource_windows.go -version $(TAG) -syso resource_windows_`go env GOARCH`.syso
 endif
@@ -59,6 +59,9 @@ endif
 	cp -av rclone`go env GOEXE` `go env GOPATH`/bin/rclone`go env GOEXE`.new
 	mv -v `go env GOPATH`/bin/rclone`go env GOEXE`.new `go env GOPATH`/bin/rclone`go env GOEXE`
 
+fetch-gui:
+	$(SHELL) ./bin/fetch-gui-dist.sh
+
 test_all:
 	go install $(LDFLAGS) $(BUILDTAGS) $(BUILD_ARGS) github.com/rclone/rclone/fstest/test_all