ProjectReference Platform Negotiation - Pass Platform Instead of PlatformTarget

[benvillalobos]

Discussed in #6871

^{Originally posted by jhennessey September 20, 2021}
I'm trying to make use of the new ProjectReference SetPlatform Negotiation feature. After performing all of the documented steps to enable the feature, I could not get a simplistic two project (non-SDK style) build to work correctly. In this case, NetFx.Library2 (x86/x64) referenced NetFx.Library1 (AnyCPU). When attempting to build, it would result with the following error:

(_CheckForInvalidConfigurationAndPlatform target) -> c:\Program Files\Microsoft Visual Studio\2022\Preview\MSBuild\Current\Bin\Microsoft.Common.CurrentVersion.targets(820 ,5): error : The BaseOutputPath/OutputPath property is not set for project 'NetFx.Library1.csproj'. Please check to ma ke sure that you have specified a valid combination of Configuration and Platform for this project. Configuration='Debug' Platform='x64'. You may be seeing this message because you are trying to build a project without a solution file, and have specified a non-default Configuration or Platform that doesn't exist for this project.

After exploring the logs and associated code changes for the feature, I could see that PlatformTarget was being passed to the referenced project here. That doesn't appease the referenced project because it uses Platform for its defined configurations. However, if I change the referenced code to pass Platform (along with PlatformTarget) my build works as expected.

Is there any reason why Platform can't also be passed to the referenced projects?

#5338
#6655

Logs:
error.log
success.log

Summarized

The long and the short of it: We should be passing Platform= instead of PlatformTarget=. There also needs to be an investigation as to whether or not we need to remove the use of PlatformTarget within the feature.