Fix TestRunDirectories crash on Android with relative/empty paths#7787

Evangelink merged 2 commits intomicrosoft:mainmicrosoft/testfx:mainfrom

jonathanpeppers:jonathanpeppers/fix-testrundirectories-android-crashjonathanpeppers/testfx:jonathanpeppers/fix-testrundirectories-android-crashCopy head branch name to clipboard