/etc/hosts
----------
To fake the buildhost, this file should contain
127.0.0.1 (buildhost) (actual hostname)

where actual hostname would be the output of "hostname" inside the build root,
and (buildhost) the name you want to turn up in the buildhost

quoting and arguments
---------------------
* the shell strips quotes from arguments, but collects stuff between quotes
  as one argument
  This means, mach build --target i686 --define "kernel 2.4.22" gets parsed as
  ['--target', 'i686', '--define', 'kernel 2.4.22']
* the shell doesn't distinguish between single or double quotes AFAICT
* this is also how python's opt parsing gets the remaining arguments
* it is safe to overquote in the shell; ie it's ok to run
  rpmbuild '--target' 'i686' '--define' 'kernel 2.4.22'
  this is what we use to execute rpmbuild calls