Fix updated GH actions (use @V3 for linux builds)

See actions/checkout#1590

Signed-off-by: falkTX <[email protected]>

.github/workflows/build.yml

@@ -48,7 +48,10 @@ jobs:
               rm *.deb
             ;;
           esac
-      - uses: actions/checkout@v4
+      # NOTE cannot use actions/checkout@v4, incompatible with ubuntu:18.04
+      # see https://github.com/actions/checkout/issues/1590
+      # https://github.com/moddevices/mod-desktop-app/actions/runs/7697857575/job/20975801114
+      - uses: actions/checkout@v3
         with:
           submodules: recursive
       - name: Set up dependencies
@@ -60,9 +63,11 @@ jobs:
             freetypepkgname="libfreetype-dev"
           fi
           apt-get install -yqq ${freetypepkgname} p7zip-full unzip wget xdg-user-dirs zip
+      # NOTE cannot use actions/cache@v3, incompatible with ubuntu:18.04
+      # https://github.com/moddevices/mod-desktop-app/actions/runs/7698414056/job/20977633093
       - name: Set up cache
         id: cache
-        uses: actions/cache@v4
+        uses: actions/cache@v3
         with:
           path: |
             ~/PawPawBuilds