Update MinGW CI to Ubuntu 20.04 (#7259)

Update MinGW CI to Ubuntu 20.04
* Use ghcr.io/lmms/linux.mingw:20.04
* Fix deprecation in ClipView.cpp
* Fix ccache and simplify git configuration
* Apply patch by @DomClark for MinGW's SDL2 target
* Update excludelist-win

.github/workflows/build.yml

@@ -153,7 +153,7 @@ jobs:
         arch: ['32', '64']
     name: mingw${{ matrix.arch }}
     runs-on: ubuntu-latest
-    container: lmmsci/linux.mingw${{ matrix.arch }}:18.04
+    container: ghcr.io/lmms/linux.mingw:20.04
     env:
       CMAKE_OPTS: >-
         -DUSE_WERROR=ON
@@ -163,12 +163,8 @@ jobs:
       CCACHE_NOCOMPRESS: 1
       MAKEFLAGS: -j2
     steps:
-      - name: Update and configure Git
-        run: |
-          add-apt-repository ppa:git-core/ppa
-          apt-get update
-          apt-get --yes install git
-          git config --global --add safe.directory "$GITHUB_WORKSPACE"
+      - name: Configure git
+        run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
       - name: Check out
         uses: actions/checkout@v3
         with:
@@ -201,7 +197,7 @@ jobs:
         run: |
           ccache --cleanup
           echo "[ccache config]"
-          ccache --print-config
+          ccache --show-config
           echo "[ccache stats]"
           ccache --show-stats
         env: