ci: install Qt-matching MinGW 13.1.0 to fix test segfaults

System MinGW on windows-latest is GCC 15.2 which has ABI mismatch
with Qt 6.8.1 (built with MinGW 13.1.0), causing all tests to
segfault. Install the matching toolchain via aqtinstall tools and
use it instead of the system compiler.

.github/workflows/build.yml

@@ -18,31 +18,32 @@ jobs:
         with:
           submodules: recursive
 
-      - name: Install Qt6
+      - name: Install Qt6 and MinGW
         uses: jurplel/install-qt-action@v4
         with:
           version: '6.8.1'
           arch: 'win64_mingw'
+          tools: 'tools_mingw1310,qt.tools.win64_mingw1310'
           cache: true
-          aqtversion: '==3.1.21'
 
       - name: Configure
         shell: bash
         run: |
-          export PATH="/c/mingw64/bin:$PATH"
+          export PATH="$IQTA_TOOLS/mingw1310_64/bin:$PATH"
+          gcc --version
           cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DBUILD_UI_TESTS=OFF \
             -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++
 
       - name: Build
         shell: bash
         run: |
-          export PATH="/c/mingw64/bin:$PATH"
+          export PATH="$IQTA_TOOLS/mingw1310_64/bin:$PATH"
           cmake --build build
 
       - name: Test
         shell: bash
         run: |
-          export PATH="/c/mingw64/bin:$PATH"
+          export PATH="$IQTA_TOOLS/mingw1310_64/bin:$PATH"
           ctest --test-dir build --output-on-failure
 
       - name: Upload artifact
@@ -115,7 +116,6 @@ jobs:
         with:
           version: '6.8.1'
           cache: true
-          aqtversion: '==3.1.21'
 
       - name: Install dependencies
         run: |