Autogenerated unittest build is incorrect for gdc and ldc

[opticron]

When using the automatically generated unittest build with dmd, -unittest is passed properly. With gdc and ldc, -funittest and -unittest are not passed properly even though they are called out in the compiler setups. This is with dub 0.9.19 for 64bit linux. This can easily be seen by passing different --compiler options.

[s-ludwig]

This has already been fixed on GIT master by #143. Will be in the 0.9.20 release in a few days.