Make build work on MacOS / BSD.

Author: Sepand Parhami

package.json

@@ -15,8 +15,8 @@
     "build-watch": "npm run build -- --watch",
     "clean": "rm -rf dist/ build/",
     "compile": "mkdir -p dist && node_modules/google-closure-compiler/cli.js -O ADVANCED --js='compile/index.js' --js='build/**.js' --js='!build/**/test-*.js' --js='!build/src/testing/**' --externs='compile/externs.js' --rewrite_polyfills=false > build/closure-output.js",
-    "create-mjs": "cp build/closure-output.js dist/animations.mjs && sed -i 's;window.\\([^=]*=\\);export const \\1;g' dist/animations.mjs",
-    "create-cjs": "cp build/closure-output.js dist/animations.js  && sed -i 's;window.\\([^=]*=\\);exports.\\1;g' dist/animations.js",
+    "create-mjs": "cp build/closure-output.js dist/animations.mjs && sed -i '' 's;window.\\([^=]*=\\);export const \\1;g' dist/animations.mjs",
+    "create-cjs": "cp build/closure-output.js dist/animations.js  && sed -i '' 's;window.\\([^=]*=\\);exports.\\1;g' dist/animations.js",
     "create-global": "npm run tsickle && npm run compile",
     "demo": "npm run build && http-server | grep -m 1 'http:\\.*' | xargs -I{} opener {}/docs/demo",
     "dist": "npm run clean && npm run create-global && npm run create-mjs && npm run create-cjs && npm run build",