Make npm clean scripts platform-agnostic

Author: murgatroid99

packages/grpc-js/package.json

@@ -44,7 +44,7 @@
   ],
   "scripts": {
     "build": "npm run compile",
-    "clean": "node -e 'require(\"rimraf\")(\"./build\", () => {})'",
+    "clean": "rimraf ./build",
     "compile": "tsc -p .",
     "format": "clang-format -i -style=\"{Language: JavaScript, BasedOnStyle: Google, ColumnLimit: 80}\" src/*.ts test/*.ts",
     "lint": "npm run check",

packages/proto-loader/package.json

@@ -14,7 +14,7 @@
   "typings": "build/src/index.d.ts",
   "scripts": {
     "build": "npm run compile",
-    "clean": "node -e 'require(\"rimraf\")(\"./build\", () => {})'",
+    "clean": "rimraf ./build",
     "compile": "tsc -p .",
     "format": "clang-format -i -style=\"{Language: JavaScript, BasedOnStyle: Google, ColumnLimit: 80}\" src/*.ts test/*.ts",
     "lint": "tslint -c node_modules/google-ts-style/tslint.json -p . -t codeFrame --type-check",