Removing Phobos dependencies from dmd test suite

[Walter Bright]

The dmd test suite is supposed to test dmd before moving on to compiling Phobos. 
This technique makes porting dmd to new platforms much easier. Unfortunately, 
many dependencies on Phobos have crept in. I've removed some:

   https://github.com/dlang/dmd/pull/9633
   https://github.com/dlang/dmd/pull/9635

If you're looking for a way to help out, there's plenty of opportunity there!

For a more challenging fix,

   test/runnable/test_cdcmp.d