CI: reduce disk usage on Ubuntu weekly build.

.github/workflows/sub_weeklyBuild.yml

@@ -59,6 +59,15 @@ jobs:
     runs-on: ${{ matrix.os }}
     environment: weekly-build
     steps:
+      # prevent running out of disk space on Ubuntu runners.
+      - name: Maximize build space
+        if: runner.os == 'Linux'
+        uses: AdityaGarg8/remove-unwanted-software@v5
+        with:
+          verbose: 'true'
+          remove-android: 'true'      # (frees ~9 GB)
+          remove-cached-tools: 'true' # (frees ~8.3 GB)
+
       - name: Set Platform Environment Variables
         shell: bash -l {0}
         env: