Windows is also always portable.

Author: crummel

repos/corefx.proj

@@ -4,9 +4,10 @@
   <PropertyGroup>
     <!-- OSX core-setup build always uses the portable RID, so override it -->
     <OverridePortableBuild>$(PortableBuild)</OverridePortableBuild>
-    <OverridePortableBuild Condition="'$(TargetOS)' == 'OSX'">true</OverridePortableBuild>
+    <OverridePortableBuild Condition="'$(TargetOS)' == 'OSX' OR '$(TargetOS)' == 'Windows_NT'">true</OverridePortableBuild>
     <OverrideTargetRid>$(TargetRid)</OverrideTargetRid>
     <OverrideTargetRid Condition="'$(TargetOS)' == 'OSX'">osx-x64</OverrideTargetRid>
+    <OverrideTargetRid Condition="'$(TargetOS)' == 'Windows_NT'">win-x64</OverrideTargetRid>
 
     <BuildArguments>-$(Configuration)</BuildArguments>
     <BuildArguments>$(BuildArguments) -buildArch=$(Platform)</BuildArguments>