interpreting variants

[Ben Elliston]

I have a target foo with a variant like foo/-mel.  How are these
variants exposed to individual test drivers so that they can intepret
the variant strings and act accordingly?  Suppose my test driver
compiles programs with an ACME compiler that requires me to compile
little endian object files using --endian=little.  What is the correct
way of making the mapping from "-mel" to "--endian-little"?  I
couldn't find anything in the documentation that covered this.

Ben