Qt/Windows: Properly link against qtmain.

Externals/Qt

@@ -1 +1 @@
-Subproject commit 63293e758fb82e675a3daa88a51407d3ccac1a9f
+Subproject commit 864c13b6664a7b44cf4142019fbf0f76a06de6de

Source/Core/DolphinQt2/Main.cpp

@@ -19,6 +19,8 @@
 #include "UICommon/CommandLineParse.h"
 #include "UICommon/UICommon.h"
 
+// N.B. On Windows, this should be called from WinMain. Link against qtmain and specify
+// /SubSystem:Windows
 int main(int argc, char* argv[])
 {
   QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

Source/VSProps/QtCompile.props

@@ -36,6 +36,7 @@
     <Link>
       <AdditionalLibraryDirectories>$(QtLibDir);%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
       <AdditionalDependencies>qtmain$(QtLibSuffix).lib;Qt5Core$(QtLibSuffix).lib;Qt5Gui$(QtLibSuffix).lib;Qt5Widgets$(QtLibSuffix).lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <SubSystem>Windows</SubSystem>
       <!--
       <AdditionalOptions>"/manifestdependency:type='Win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\" %(AdditionalOptions)</AdditionalOptions>
       -->