ci: use cmake toolchain file instead of missing mingw64-cmake

.gitea/workflows/build-windows-release.yml

@@ -48,7 +48,6 @@ jobs:
             cmake \
             ninja-build \
             mingw64-gcc-c++ \
-            mingw64-cmake \
             mingw64-qt6-qtbase \
             mingw64-qt6-qtimageformats \
             mingw64-opencv
@@ -58,7 +57,8 @@ jobs:
 
       - name: Configure cross build
         run: |
-          x86_64-w64-mingw32-cmake -S . -B build-windows -G Ninja \
+          cmake -S . -B build-windows -G Ninja \
+            -DCMAKE_TOOLCHAIN_FILE=/usr/share/mingw/toolchain-mingw64.cmake \
             -DCMAKE_BUILD_TYPE="$BUILD_TYPE"
 
       - name: Build