windows/msvc/paths.props: Dont add variant path to PyIncDirs.

This file is shared by mpy-cross.vcxproj, where PyVariant will be not set
(because common.props explicitly doesn't set it when building mpy-cross).

Update common.props to only add the variant path to PyIncDirs if not
building mpy-cross.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/windows/msvc/common.props

@@ -19,6 +19,9 @@
     <PyFileCopyCookie>$(PyBuildDir)copycookie$(Configuration)$(Platform)</PyFileCopyCookie>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
+  <PropertyGroup Condition="'$(PyBuildingMpyCross)' != 'True'">
+    <PyIncDirs>$(PyIncDirs);$(PyVariantDir)</PyIncDirs>
+  </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
       <AdditionalIncludeDirectories>$(PyIncDirs);%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>

ports/windows/msvc/paths.props

@@ -31,8 +31,8 @@
     <PyVariantDir Condition="'$(PyVariantDir)' == ''">$(PyWinDir)variants\$(PyVariant)\</PyVariantDir>
     <PyTargetDir Condition="'$(PyTargetDir)' == ''">$(PyBuildDir)</PyTargetDir>
 
-    <!-- All include directories needed for uPy -->
-    <PyIncDirs>$(PyIncDirs);$(PyBaseDir);$(PyWinDir);$(PyBuildDir);$(PyWinDir)msvc;$(PyVariantDir)</PyIncDirs>
+    <!-- Common include directories needed for uPy -->
+    <PyIncDirs>$(PyIncDirs);$(PyBaseDir);$(PyWinDir);$(PyBuildDir);$(PyWinDir)msvc</PyIncDirs>
 
     <!-- Within PyBuildDir different subdirectories are used based on configuration and platform.
          By default these are chosen based on the Configuration and Platform properties, but