anchor.diff:      let cmd',args' = if Xake.Env.isUnix then "mono", cmd::args else cmd,args
       in system cmd' args'
   
  -do xake {ExecOptions.Default with FileLog = "build.log"; ConLogLevel = Verbosity.Chatty } {
  +do xake {ExecOptions.Default with Vars = ["NETFX", "mono-40"]; FileLog = "build.log"; ConLogLevel = Verbosity.Chatty } {
   
       rules [
           "all"  => action {
  
positive.code:                     Out = file
                      Src = sources
                      Ref = !! "bin/FSharp.Core.dll"
                      TargetFramework = "4.0"
                      RefGlobal = ["mscorlib.dll"; "System.dll"; "System.Core.dll"; "System.Windows.Forms.dll"]
                      Define = ["TRACE"]
                      CommandArgs = ["--optimize+"; "--warn:3"; "--warnaserror:76"; "--utf8output"]
  
negative.code:         "bin/Xake.Core.dll" *> fun file -> action {
  
              // TODO --doc:..\bin\Xake.Core.XML --- multitarget rule!
  
              let sources = fileset {
                  basedir "core"
                  includes "Logging.fs"
  