Add a test cases for 9.4 and 10.0 betas.

[jerrymarino]

This tool may need some work and testing to work with the latest Xcode releases and betas. See the discussion here for more info https://github.com/jerrymarino/SwiftVimTestHost/issues/1

[jerrymarino]

Since this program is pretty much required to use iCompleteMe with Xcode, I took the liberty to rework it so it will work with the new build system in 10.0 and 9.4 and be more robust in general.

https://github.com/jerrymarino/XcodeCompilationDatabase/pull/5 is tested case for 9.4 on both new and old build systems 🎉 . I'll call this done when it works for the latest beta of 10.0.

[fenglh]

not work in xcode 11.4