Report TFM via GetTargetFrameworks if TF undefined#3550

rainersigwald wants to merge 2 commits intodotnet:vs15.9stgdotnet/msbuild:vs15.9stgfrom

rainersigwald:support-non-sdk-projects-in-tf-compat-checkrainersigwald/msbuild:support-non-sdk-projects-in-tf-compat-checkCopy head branch name to clipboard