fixing a test to also work in Windows

used to do this:
'MIX_ENV' is not recognized as an internal or external command,
operable program or batch file.
Tested to work on both Windows and Linux.
However the following is seen on console:
Mix requires the compile path "ebin" to be inside a directory with the
 same name as the application name :no_mixfile,
got "s:/workspace.elixir.2013/elixir/lib/mix/tmp/Mix.CLITest/test env/ebin"

quick test with `make test_mix`


I notice I forgot to put spaces around the `=` should I add a new commit fixing those or how would you go about doing that if it were necessary (assuming extra commits are not an option)? (and I forgot an extra word there `afterwards`)