No error when library is missing

[back2dos]

The build just completely stops here: https://travis-ci.org/haxetink/tink_tcp/jobs/129677819#L1424

The reason is that tink_runloop was not in fact installed. Obviously this seems more of a Travis oddity (at the very least one would expect a haxelib run travix neko -lib tink_runloop exited with <error code>), but we should have some output anyway.

Also, travix could actually install the library and move on.

[kevinresol]

Can we merge those extra arguments with the tests.hxml and write a temp.hxml, then we can haxelib install and then haxe on that. And after that we just delete the temp.hxml?