CI: gzip intermediate stage tarballs to reduce network usage

.github/workflows/bwrap.yml

@@ -51,12 +51,12 @@ jobs:
           name: packages
           path: tmp/external/repo/**
       - name: Tar pass1 image
-        run: tar -cf pass1_image.tar tmp
+        run: tar -czf pass1_image.tar.gz tmp
       - name: Archive pass1_image
         uses: actions/upload-artifact@v3
         with:
           name: internal_pass1_image
-          path: pass1_image.tar
+          path: pass1_image.tar.gz
 
   pass2:
     name: Run up to Python bootstrap under bubblewrap
@@ -77,7 +77,7 @@ jobs:
         with:
           name: internal_pass1_image
       - name: Extract pass1_image
-        run: tar -xf pass1_image.tar
+        run: tar -xzf pass1_image.tar.gz
       - name: Query cache for sources
         id: cache
         uses: actions/cache/restore@v3
@@ -104,12 +104,12 @@ jobs:
           name: internal_packages_pass2
           path: tmp/external/repo/**
       - name: Tar pass2 image
-        run: tar -cf pass2_image.tar tmp
+        run: tar -czf pass2_image.tar.gz tmp
       - name: Archive pass2_image
         uses: actions/upload-artifact@v3
         with:
           name: internal_pass2_image
-          path: pass2_image.tar
+          path: pass2_image.tar.gz
 
   pass3:
     name: Run remaining builds under bubblewrap
@@ -130,7 +130,7 @@ jobs:
         with:
           name: internal_pass2_image
       - name: Extract pass2_image
-        run: tar -xf pass2_image.tar
+        run: tar -xzf pass2_image.tar.gz
       - name: Query cache for sources
         id: cache
         uses: actions/cache/restore@v3