[mono] Fix build by correctly setting the TargetFramework for
[mono] Fix build by correctly setting the TargetFramework for

.. Build.csproj .

cdmihai/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,jeffkl/msbuild,chipitsine/msbuild,chipitsine/msbuild,jeffkl/msbuild,Microsoft/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,cdmihai/msbuild,Microsoft/msbuild,mono/msbuild,cdmihai/msbuild,jeffkl/msbuild,Microsoft/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,mono/msbuild,sean-gilliam/msbuild,Microsoft/msbuild,chipitsine/msbuild,chipitsine/msbuild,rainersigwald/msbuild,mono/msbuild,mono/msbuild,AndyGerlicher/msbuild,jeffkl/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild