Make Android NDK discovery more robust, and add tests#659

jakepetroules merged 1 commit intoswiftlang:mainswiftlang/swift-build:mainfrom

jakepetroules:eng/PR-android-ndk-improvements-release/6.2jakepetroules/swift-build:eng/PR-android-ndk-improvements-release/6.2Copy head branch name to clipboard