Fix build on linux

[savornicesei]

Fail quite expected ...

Sistem

$> dotnet --version
2.2.203
$> mono --version
Mono JIT compiler version 5.20.1.19 (tarball Mon Apr 15 10:29:30 UTC 2019)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
        TLS:           __thread
        SIGSEGV:       altstack
        Notifications: epoll
        Architecture:  amd64
        Disabled:      none
        Misc:          softdebug 
        Interpreter:   yes
        LLVM:          supported, not enabled.
        Suspend:       hybrid
        GC:            sgen (concurrent by default)
$> uname -a
Linux devrog.avornicesei.com 5.0.9-1-default #1 SMP Sun Apr 21 06:42:32 UTC 2019 (7bd8353) x86_64 x86_64 x86_64 GNU/Linux
$> dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   2.2.203
 Commit:    e5bab63eca

Runtime Environment:
 OS Name:     opensuse-tumbleweed
 OS Version:  20190426
 OS Platform: Linux
 RID:         linux-x64
 Base Path:   /usr/share/dotnet/sdk/2.2.203/

Host (useful for support):
  Version: 2.2.4
  Commit:  f95848e524

.NET Core SDKs installed:
  2.1.502 [/usr/share/dotnet/sdk]
  2.2.203 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.6 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.6 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.6 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.4 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

Log

nant-build.log