Invoke PrivateP2PCaching.proj fewer times

* We can invoke it once instead of twice by invoking the two targets we need in one MSBuild call. Only a small gain expected by this.
* We are more careful to keep the set of global properties the same across many project invocations so that we don't get multiple project instances with global properties such as Configuration and Platform that may vary by caller.

Closes #1262

Author: AArnott

src/Nerdbank.GitVersioning.Tasks/build/MSBuildTargetCaching.targets

@@ -22,7 +22,7 @@
   <ItemGroup>
     <NBGV_CachingProjectReference Include="$(NBGV_CachingProjectReference)">
       <Targets>GetBuildVersion_Properties;GetBuildVersion_CloudBuildVersionVars</Targets>
-      <Properties>$(NBGV_InnerGlobalProperties)BuildMetadata=@(BuildMetadata, ',');PrereleaseIdentifiers=@(PrereleaseIdentifier, ',')</Properties>
+      <Properties>$(NBGV_InnerGlobalProperties)BuildMetadata=@(BuildMetadata, ',');PrereleaseIdentifiers=@(PrereleaseIdentifier, ',');Configuration=Release;Platform=AnyCPU</Properties>
       <SetConfiguration>Configuration=Release</SetConfiguration>
       <SetPlatform>Platform=AnyCPU</SetPlatform>
       <GlobalPropertiesToRemove>@(NBGV_GlobalPropertiesToRemove)</GlobalPropertiesToRemove>
@@ -50,18 +50,14 @@
     <!-- Calculate version by invoking another "project" with global properties that will serve as a key
          into an msbuild cache to ensure we only invoke the GetBuildVersion task as many times as will produce a unique value. -->
     <MSBuild Projects="@(NBGV_CachingProjectReference)"
-             Properties="%(NBGV_CachingProjectReference.Properties)"
              RemoveProperties="%(NBGV_CachingProjectReference.GlobalPropertiesToRemove)"
-             Targets="GetBuildVersion_Properties">
-      <Output TaskParameter="TargetOutputs" ItemName="NBGV_PropertyItems" />
+             Targets="GetBuildVersion_Properties;GetBuildVersion_CloudBuildVersionVars">
+      <Output TaskParameter="TargetOutputs" ItemName="_NBGV_PropertiesAndVersionVars" />
     </MSBuild>
 
-    <!-- Also get other items. -->
-    <MSBuild Projects="@(NBGV_CachingProjectReference)"
-             Properties="%(NBGV_CachingProjectReference.Properties)"
-             RemoveProperties="%(NBGV_CachingProjectReference.GlobalPropertiesToRemove)"
-             Targets="GetBuildVersion_CloudBuildVersionVars">
-      <Output TaskParameter="TargetOutputs" ItemName="CloudBuildVersionVars" />
-    </MSBuild>
+    <ItemGroup>
+      <NBGV_PropertyItems Include="@(_NBGV_PropertiesAndVersionVars)" Condition="'%(MSBuildSourceTargetName)'=='GetBuildVersion_Properties'" />
+      <CloudBuildVersionVars Include="@(_NBGV_PropertiesAndVersionVars)" Condition="'%(MSBuildSourceTargetName)'=='GetBuildVersion_CloudBuildVersionVars'" />
+    </ItemGroup>
   </Target>
 </Project>