make build-gui script work on all platforms

Author: Christopher Willis-Ford

package.json

@@ -7,7 +7,7 @@
   "license": "BSD-3-Clause",
   "scripts": {
     "start": "electron-webpack dev --bail --display-error-details --env.minify=false",
-    "build-gui": "cd ./node_modules/scratch-gui && BUILD_MODE=dist STATIC_PATH=static npm run build",
+    "build-gui": "node ./scripts/build-gui.js",
     "clean": "rimraf ./dist/ ./static/assets/",
     "compile": "rimraf ./dist/ && electron-webpack --bail --display-error-details --env.minify=false",
     "fetch": "rimraf ./static/assets/ && mkdirp ./static/assets/ && node ./scripts/fetchMediaLibraryAssets.js",

scripts/build-gui.js

@@ -0,0 +1,15 @@
+const childProcess = require('child_process');
+const path = require('path');
+
+childProcess.spawnSync(
+    'npm', ['run', 'build'],
+    {
+        cwd: path.join('node_modules', 'scratch-gui'),
+        env: {
+            BUILD_MODE: 'dist',
+            STATIC_PATH: 'static'
+        },
+        shell: true,
+        stdio: 'inherit'
+    }
+);