Fix building on non windows with mono

[BitPuffin]

Setting the version to mono-2.0 for microsoft build tasks breaks the build. Because it tries to override something which I guess wasn't in 2.0

[BitPuffin]

Boo.Microsoft.Build.Tasks:

 [property] Target framework changed to "Mono 2.0 Profile".
     [booc] Compiling 2 files to '/Users/isak/src/csharp/boo/build/Boo.Microsoft.Build.Tasks.dll'.
     [booc] /Users/isak/src/csharp/boo/src/Boo.Microsoft.Build.Tasks/Booc.boo(210,28): BCE0060: 'Boo.Microsoft.Build.Tasks.Booc.LogEventsFromTextOutput(string, Microsoft.Build.Framework.MessageImportance)': no suitable method found to override.
     [booc] /Users/isak/src/csharp/boo/src/Boo.Microsoft.Build.Tasks/Booc.boo(255,9): BCE0061: 'Boo.Microsoft.Build.Tasks.Booc.LogEventsFromTextOutput(string, Microsoft.Build.Framework.MessageImportance)' is not an override.
     [booc] 2 error(s).

BUILD FAILED - 0 non-fatal error(s), 43 warning(s)

that^

[BitPuffin]

Hmm strange that it failed with travis. Works on OS X

mono --version
Mono JIT compiler version 4.2.1 (Stable 4.2.1.102/6dd2d0d Wed Nov 18 17:03:43 PST 2015)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
    TLS:           normal
    SIGSEGV:       altstack
    Notification:  kqueue
    Architecture:  amd64
    Disabled:      none
    Misc:          softdebug
    LLVM:          supported, not enabled.
    GC:            sgen

[drslump]

I'm having the same issue with mono 4.2.0 on OS X. To me forcing the framework to mono-4.0 fixes the issue. It looks like this:

<property name="nant.settings.currentframework" value="mono-4.0" unless="${platform::is-windows()}" />

[BitPuffin]

Travis is still unhappy :(

[BitPuffin]

Well with travis it is probably just that it's installing mono 3.12

[drslump]

I'm trying with 4.20 and 3.12 (in OSX though) and both work properly. I'll check updating the nant version used in Travis, perhaps that's the issue.

[drslump]

I've spent hours on this and haven't been able to figure out why it's failing in 3.12. The bundled Mono assembly in that version must be broken or something I guess.

I'm closing this PR in favour of https://github.com/boo-lang/boo/pull/128 which upgrades Travis to run on Mono 4.2.1.

Thanks!