Switch to Qt 5.9.4

.appveyor.yml

@@ -15,7 +15,7 @@ environment:
 install:
   - git submodule update --init --recursive
   - call "%ProgramFiles(x86)%\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x86
-  - set PATH=C:\Qt\Tools\QtCreator\bin;C:\Qt\5.9.3\msvc2015\bin;%PATH%
+  - set PATH=C:\Qt\Tools\QtCreator\bin;C:\Qt\5.9.4\msvc2015\bin;%PATH%
   - mkdir %LOCALAPPDATA%\QtProject && copy test\qtlogging.ini %LOCALAPPDATA%\QtProject\
   - ps: |
       Write-Host "Installing GStreamer..." -ForegroundColor Cyan
@@ -35,7 +35,7 @@ install:
       Write-Host "Installed" -ForegroundColor Green
 
 build_script:
-  - mkdir %SHADOW_BUILD_DIR% && cd %SHADOW_BUILD_DIR% && C:\Qt\5.9.3\msvc2015\bin\qmake -r CONFIG-=debug_and_release CONFIG+=%CONFIG% CONFIG+=WarningsAsErrorsOn %APPVEYOR_BUILD_FOLDER%\qgroundcontrol.pro
+  - mkdir %SHADOW_BUILD_DIR% && cd %SHADOW_BUILD_DIR% && C:\Qt\5.9.4\msvc2015\bin\qmake -r CONFIG-=debug_and_release CONFIG+=%CONFIG% CONFIG+=WarningsAsErrorsOn %APPVEYOR_BUILD_FOLDER%\qgroundcontrol.pro
   - cd %SHADOW_BUILD_DIR% && jom
   - if "%CONFIG%" EQU "installer" ( copy %SHADOW_BUILD_DIR%\release\QGroundControl-installer.exe %APPVEYOR_BUILD_FOLDER%\QGroundControl-installer.exe )
 # Generate the source server information to embed in the PDB