It couldn't find mcs. Pic is from the original linux launcher. mcs needs to symlink to something. Question is what in this setup.
@thfr @canadianbryan @mulander @bcallah I'm no Mono internals expert, but I believe what's happening is XML serialization is calling mcs; the question is why is it asking to compile an assembly? I would think it should be able to reflect inside the assembly. (Stupid guess: is the serializing thinking it can't find a class to make outside the assembly?)
That being said... what parameters is it passing to mcs? FWIW, mcs is a script to call mono mcs.exe, so make sure that's in working order, OFC.