Fix include and library path locations for when the project file is not in src/*

e.g. src/sbbs3/scfg/scfg.vcxproj

src/build/sdl.props

@@ -6,10 +6,10 @@
   <ItemDefinitionGroup>
     <ClCompile>
       <PreprocessorDefinitions>WITH_SDL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-      <AdditionalIncludeDirectories>..\..\3rdp\win32.release\sdl\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>$(MSBuildThisFileDirectory)..\..\3rdp\win32.release\sdl\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
-      <AdditionalLibraryDirectories>..\..\3rdp\win32.release\sdl\lib\x86;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
+      <AdditionalLibraryDirectories>$(MSBuildThisFileDirectory)..\..\3rdp\win32.release\sdl\lib\x86;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
     </Link>
     <Link>
       <AdditionalDependencies>SDL.lib;%(AdditionalDependencies)</AdditionalDependencies>

src/build/sdl2.props

@@ -6,10 +6,10 @@
   <ItemDefinitionGroup>
     <ClCompile>
       <PreprocessorDefinitions>WITH_SDL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-      <AdditionalIncludeDirectories>..\..\3rdp\win32.release\sdl2\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>$(MSBuildThisFileDirectory)..\..\3rdp\win32.release\sdl2\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
-      <AdditionalLibraryDirectories>..\..\3rdp\win32.release\sdl2\lib\x86;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
+      <AdditionalLibraryDirectories>$(MSBuildThisFileDirectory)..\..\3rdp\win32.release\sdl2\lib\x86;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>
     </Link>
     <Link>
       <AdditionalDependencies>SDL2.lib;%(AdditionalDependencies)</AdditionalDependencies>