Problem: vc common props have platform specific conditions.

builds/msvc/properties/Common.props

@@ -18,11 +18,4 @@
     </ClCompile>
   </ItemDefinitionGroup>
 
-  <!-- When using a tool set to target Windows XP, define a pre-processor definition and modify the target Windows version -->
-  <ItemDefinitionGroup Condition="$(PlatformToolset.Contains('_xp'))">
-    <ClCompile>
-      <PreprocessorDefinitions>ZMQ_HAVE_WINDOWS_TARGET_XP;_WIN32_WINNT=0x0501;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-    </ClCompile>
-  </ItemDefinitionGroup>
-
 </Project>
\ No newline at end of file