0029571: Samples: build qt samples together with OCCT

Extending CMake procedure by 'BUILD_MODULE_QtSamples' variable to switch on qt samples build.
Implementation required:
- union of occt_toolkit_tool.cmake and occt_toolkit.cmake files;
- correction of qt samples sources by adding path to Qt 'plugins' folder. It helps to avoid definition of additional variable (QT_QPA_PLATFORM_PLUGIN_PATH) when staring sample.bat for qt samples;
- executable processing is extended in cmake procedure by providing 'EXECUTABLE_PROJECT' variable. Now we need not specify custom processing for DRAWEXE in occt_toolkit.cmake

samples/qt/IESample/src/FILES

@@ -0,0 +1 @@
+Main.cxx

samples/qt/IESample/src/Main.cxx

@@ -1,15 +1,20 @@
 #include "Application.h"
 
+#include <OSD_Environment.hxx>
+
 #include <QApplication>
 #include <QTranslator>
 #include <QPixmap>
 #include <QLocale>
   
 
-
 int main ( int argc, char* argv[] )
 {
-  
+#if QT_VERSION > 0x050000
+  TCollection_AsciiString aPlugindsDirName = OSD_Environment ("QTDIR").Value();
+  if (!aPlugindsDirName.IsEmpty())
+    QApplication::addLibraryPath (QString (aPlugindsDirName.ToCString()) + "/plugins");
+#endif
   QApplication a( argc, argv );
 
   QString resDir = ApplicationCommonWindow::getResourceDir();