Add parametrized build script

[ci skip]

build-scripts/pkg-support/msvc/Directory.Build.props

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemDefinitionGroup>
+    <ClCompile>
+      <PreprocessorDefinitions>SDL_VENDOR_INFO="libsdl.org";%(PreprocessorDefinitions)</PreprocessorDefinitions>
+    </ClCompile>
+  </ItemDefinitionGroup>
+</Project>