fix: use Bash shell and omit rm errors (#13)

Without this change, if the user does not have bash, `command` fails (as
it is a bash built-in). Explicitly set bash to be the shell.

Omit error messages of the `rm` command while cleaning.

Makefile

@@ -1,5 +1,6 @@
 EMACS ?= emacs
 SHELL = bash
+
 CASK ?= $(shell command -v cask)
 ifeq ($(CASK),)
     $(error "Install cask (https://github.com/cask/cask)")
@@ -41,11 +42,11 @@ test: zmq compile
 .PHONY: clean
 clean:
 	make -C js clean
-	rm $(ELCFILES)
+	@rm $(ELCFILES) 2>/dev/null || true
 
 .PHONY: clean-cask
 clean-cask:
-	rm -rf .cask/
+	@rm -rf .cask/ 2>/dev/null || true
 
 .PHONY: widgets
 widgets:

js/Makefile

@@ -1,3 +1,5 @@
+SHELL = bash
+
 NPM ?= $(shell command -v npm)
 ifeq ($(NPM),)
 	$(error "Node not installed (https://nodejs.org/en/)")
@@ -14,10 +16,10 @@ endif
 all: build
 
 clean:
-	rm -rf built/
+	@rm -rf built/ 2>/dev/null || true
 
 really-clean: clean
-	rm -rf node_modules
+	@rm -rf node_modules 2>/dev/null || true
 
 build: built/index.built.js