ci: use sccache on windows

This apparently works with less hacks, and is actually suggested by the
action we're using

Signed-off-by: Seth Flynn <getchoo@tuta.io>

.github/actions/setup-dependencies/action.yml

@@ -53,9 +53,20 @@ runs:
       if: ${{ (runner.os != 'Windows' || inputs.msystem == '') && inputs.build-type == 'Debug' }}
       uses: hendrikmuhs/ccache-action@v1.2.17
       with:
+        variant: ${{ runner.os == 'Windows' && 'sccache' || 'ccache' }}
         create-symlink: ${{ runner.os != 'Windows' }}
         key: ${{ runner.os }}-qt${{ inputs.qt_ver }}-${{ inputs.architecture }}
 
+    - name: Use ccache on debug builds
+      if: ${{ inputs.build-type == 'Debug' }}
+      shell: bash
+      env:
+        # Only use sccache on MSVC
+        CCACHE_VARIANT: ${{ (runner.os == 'Windows' && inputs.msystem == '') && 'sccache' || 'ccache' }}
+      run: |
+        echo "CMAKE_C_COMPILER_LAUNCHER=$CCACHE_VARIANT" >> "$GITHUB_ENV"
+        echo "CMAKE_CXX_COMPILER_LAUNCHER=$CCACHE_VARIANT" >> "$GITHUB_ENV"
+
     - name: Install Qt
       if: ${{ inputs.msystem == '' }}
       uses: jurplel/install-qt-action@v4