Overriding emchain to select a gcc version

[Brendan Simon <Brendan@BrendanSimon.com>]

Can emchain select which version of gcc to build.  By default it builds 
the latest gcc in the target suite.  So for testing that is gcc-4.3.0~rc2-1.
But what if I want to build gcc-4.2 in testing (gcc-4.2.3-2) ??
Can I set some configuration or command line switch to override the default?

Thanks, Brendan.