Adding condition for default TargetPlatform properties (#5391)
Adding condition for default TargetPlatform properties (#5391)

Adding a condition for setting default TargetPlatform properties. `_EnableDefaultWindowsPlatform` will be set from the SDK in a separate PR
AndyGerlicher/msbuild,rainersigwald/msbuild,mono/msbuild,AndyGerlicher/msbuild,mono/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,mono/msbuild,cdmihai/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,cdmihai/msbuild,cdmihai/msbuild,cdmihai/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,mono/msbuild,sean-gilliam/msbuild