$ cat > test.cs <<EOF
using System;
namespace MyFirstConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
        }
    }
}
EOF
$ mcs test.cs
$ mono --optimize=precomp test.exe
cant resolve internal call to "System.Threading.ThreadPool::PostQueuedCompletionStatus(System.Threading.NativeOverlapped*)" (tested without signature also)

Your mono runtime and class libraries are out of sync.
The out of sync library is: /usr/lib/mono/4.5/mscorlib.dll

When you update one from git you need to update, compile and install
the other too.
Do not report this as a bug unless you're sure you have updated correctly:
you probably have a broken mono install.
If you see other errors or faults after this message they are probably related
and you need to fix your mono install first.
cant resolve internal call to "System.Threading.ThreadPool::PostQueuedCompletionStatus(System.Threading.NativeOverlapped*)" (tested without signature also)

Your mono runtime and class libraries are out of sync.
The out of sync library is: /usr/lib/mono/4.5/mscorlib.dll

When you update one from git you need to update, compile and install
the other too.
Do not report this as a bug unless you're sure you have updated correctly:
you probably have a broken mono install.
If you see other errors or faults after this message they are probably related
and you need to fix your mono install first.
Hello World!

Система: ALT Workstation 9.1 x86_64, текущий сизиф
Версия пакета: mono-core-6.12.0.122-alt1