fix(ci): add temp arm64 workaround

currently required, because Flatpak arm64 build currently fails – and if it fails, the remaining builds (deb, rpm, zip) fail as well, as they are created in the same run.
once the fix is released in the next electron-forge, we can get rid of this again.

.github/actions/build-electron/action.yml

@@ -27,6 +27,10 @@ runs:
     - name: Install dependencies
       shell: bash
       run: npm ci
+    - name: Temporary Flatpak arm64 workaround till https://github.com/electron/forge/pull/3839 is merged
+      if: ${{ inputs.os == 'linux' && inputs.arch == 'arm64' }}
+      shell: bash
+      run:  sed -e "s/case 'armv7l'/case 'arm64'/g" -e "s/return 'arm'/return 'aarch64'/g" -i node_modules/@electron-forge/maker-flatpak/dist/MakerFlatpak.js
     - name: Update build info
       shell: bash
       run: npm run update-build-info