cleanup some space before docker build

Author: stephen-derosa

.github/workflows/builds.yml

@@ -266,6 +266,18 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
+      # Default ubuntu-latest images are tight on disk; this Dockerfile builds GCC
+      # from source plus Rust — BuildKit export/import needs several extra GB.
+      - name: Free disk space
+        uses: jlumbroso/free-disk-space@v1.3.1
+        with:
+          tool-cache: false
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: true
+          swap-storage: true
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
@@ -305,6 +317,16 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
+      - name: Free disk space
+        uses: jlumbroso/free-disk-space@v1.3.1
+        with:
+          tool-cache: false
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: true
+          swap-storage: true
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3