Fix case where dependent target, needed to evaluate condition, is skipped because condition is false.

[jlaanstra]

MSBuild won't run targets listed in DependsOnTargets if the target is skipped due to a false condition.

In this case, the condition to run the MakeReferenceProjection input is dependent on one of the DependsOnTargets targets, causing an issue in cases where that target didn't run earlier.

The fix is a technique recommended by the MSBuild team and already used elsewhere in the targets file:

<Target Name="X" DependsOnTargets="_DetermineIfA;_A" />
<Target Name="_DetermineIfA">
  <!-- set properties -->
</Target>
<Target Name="_A" Condition="whatever" />

We apply this by having a CppWinRTResolveReferences target and have the MakeReferenceProjections target have a dependency on this new target.

Tested

• NuGetTest.sln (Vs/MSBuild)
• Various razzle projects.

Fixes #395