MSBuild add log file support

[patriksvensson]

Would be nice if we could add file logging to MSBuild calls.

msbuild.exe /fl1 /fl2 /fl3
            /flp1:logfile=MyProjectOutput1.log;verbosity=diagnostic 
            /flp2:logfile=MyProjectOutput2.log;verbosity=minimal
            /flp3:logfile=MyProjectOutput3.log;Append;errorsonly;Encoding=UTF-8

Maybe we can represent the settings with something like this:

public sealed class MSBuildFileLoggerSettings
{
  public FilePath LogFile { get; set; }
  public Verbosity Verbosity { get; set; }
  public bool ErrorsOnly { get; set; }
  public bool WarningsOnly { get; set; }
  public bool Append { get; set; }
  public Encoding Encoding { get; set; }
}

(This should obviously be discussed before implementation since there's probably is a nicer way of doing this)

And add it to the settings.

MSBuild("./myproject.sln", new MSBuildSettings()
  .AddFileLogger(new MSBuildFileLoggerSettings {
    LogFile = "./errors.txt",
    ErrorsOnly = true   
  })

[gep13]

@patriksvensson is this related to this: #702

[patriksvensson]

@gep13 No, it's two different things.