OS X 10.11 El Capitan Beta and Xamarin / Compiler Error 127

Just for those of you, who can't wait to install the beta of OS X 10.11 El Capitan:

When building with Xamarin Studio, the Error 127 appeared.

For me, this solved it:

1. Restart the Mac with cmd-r pressed and go to security-settings in the rescue-mode.
2. Deselect "Force system integrity protection"
3. Restart the Mac and recopy the mcs-file with the following command:

sudo cp /Library/Frameworks/Mono.framework/Commands/mcs /usr/bin/

In my case, now everything works fine! Just wanted to share this ...