[Omake] Order of evaluation

[Benjamin Pierce]

OK, here's today's question... :-)

One of the generated modules in the Harmony build can be constructed  
in either of two ways:
    - When we're building a binary that's going to be installed  
elsewhere in the filesystem,
      this module gets built from a whole bunch of other files in a  
complicated way.
    - When we're building a binary that's going to be used "in  
place" (i.e., during testing),
      we can get by with a stub version of this module that has no  
dependencies.

In GNU Make, I would handle this situation like this (in pseudocode,  
since I'm trying to forget make syntax :-)...

    .PHONY: fast slow

    fast:
	make $(RESULT) FAST=true

    slow:
	make $(RESULT) FAST=false

    if FAST=true then
         foo.ml:
	     cp foo.ml.fast foo.ml
    else
	foo.ml: <lots of dependencies>
	     <complicated stuff>
    fi

    $(RESULT): foo.o ...
	<regular compile and link stuff>

But in OMake I can't do the recursive invocation, so this can't be  
translated directly.  I could just give the FAST flag on the command  
line every time (typing "omake FAST=true"), but this is a lot of  
typing, compared to just "omake fast", for something I'm going to do  
a lot.  (Moreover, what I really want is not just "fast" and "slow"  
targets: e.g., I want to incorporate the "slow" stuff into a larger  
"omake install" behavior...)

What would be the most idiomatic way to do this?

Thanks!

     - Benjamin