use mirror for install-qt-action (#3070)

.github/workflows/CI-unixish.yml

@@ -43,6 +43,7 @@ jobs:
         uses: jurplel/install-qt-action@v2
         with:
           modules: 'qtcharts'
+          mirror: 'http://mirrors.ocf.berkeley.edu/qt/'
 
       - name: Test CMake build
         run: |

.github/workflows/CI-windows.yml

@@ -57,6 +57,7 @@ jobs:
         uses: jurplel/install-qt-action@v2
         with:
           modules: 'qtcharts'
+          mirror: 'http://mirrors.ocf.berkeley.edu/qt/'
 
       - name: Build GUI x64 release
         run: |

.github/workflows/release-windows.yml

@@ -53,6 +53,7 @@ jobs:
         with:
           version: '5.15.2'
           modules: 'qtcharts qthelp'
+          mirror: 'http://mirrors.ocf.berkeley.edu/qt/'
 
       - name: Create .qm
         run: |