Always minify JS files and add NODE_ENV production on release targets

Makefile

@@ -97,6 +97,7 @@ release-sources:
 	git archive --format zip --output web-ext-artifacts/$$dest-sources.zip $(shell git rev-parse --abbrev-ref HEAD)
 
 .PHONY: release-firefox
+release-firefox: export NODE_ENV=production
 release-firefox: clean source-lint source-build moz-lint
 	test -d web-ext-artifacts || mkdir web-ext-artifacts
 	set -e ;\
@@ -107,6 +108,7 @@ release-firefox: clean source-lint source-build moz-lint
 	--overwrite-dest
 
 .PHONY: release-chrome
+release-chrome: export NODE_ENV=production
 release-chrome: export TARGET_BROWSER=chrome
 release-chrome: clean source-lint source-build
 	test -d web-ext-artifacts || mkdir web-ext-artifacts

gulpfile.js

@@ -66,8 +66,7 @@ function js_bundle(done) {
           platform: "browser",
           logLevel: "warning",
           metafile: false,
-          minifyIdentifiers: process.env.NODE_ENV == "production",
-          minifyWhitespace: process.env.NODE_ENV == "production",
+          minify: true,
           banner: {
             js: "//" + LICENSE_HEADER.join("\n//"),
           },