Running build.sh (specifically on Ubuntu 12.04, in a 32-bit install) I immediately run into this error:
Cannot open assembly '/opt/fogbugz/Tools/wasabi/wasabi.exe': No such file or directory.
This appears to be because the installer creates /opt/fogbugz/Tools/Wasabi. Note the case difference. I can only assume this was a typo in either the folder name or build script. Either way, pointing the script to the right folder (by either editing the script, symlinking 'wasabi' to 'Wasabi', or outright copying/moving the folder in question) and the build script chugs along merrily!