VS: Drop GenerateManifest from .vcxproj files for non-MS tools

The .vcxproj file content generated by OutputLinkIncremental is
specific to MS tools, so drop it when using other tools.

Source/cmVisualStudio10TargetGenerator.cxx

@@ -1593,6 +1593,10 @@ void
 cmVisualStudio10TargetGenerator::
 OutputLinkIncremental(std::string const& configName)
 {
+  if(!this->MSTools)
+    {
+    return;
+    }
   // static libraries and things greater than modules do not need
   // to set this option
   if(this->Target->GetType() == cmTarget::STATIC_LIBRARY