Clean Yarn cache during Electron builds

scripts/electron-package.sh

@@ -85,6 +85,11 @@ if [ -n "$conffile" ]; then
     pushd "$builddir"
 fi
 
+# We use Git branch / commit dependencies for some packages, and Yarn seems
+# to have a hard time getting that right. See also
+# https://github.com/yarnpkg/yarn/issues/4734. As a workaround, we clean the
+# global cache here to ensure we get the right thing.
+yarn cache clean
 yarn install
 yarn build:electron