Re: mirari updates

[Thomas Gazagnaire <thomas.gazagnaire@xxxxxxxxx>]

>> That's a really nice feature! I think what Vincent was looking for (correct 
>> me if I'm wrong, Vincent) is the way to run arbitrary commands without 
>> switching back and forth between compilers. I'm thinking of:
>> 
>> $ opam config env --switch 4.01.0+mirage-xen -- obuild build
>> 
>> So that I can do a mirage build in my current dir, but still use the system 
>> compiler, for instance. This would be a useful feature outside of mirari.
> 
> That's correct: we currently don't have a way to spawn a subshell with the 
> environment variables for a different switch.  Note that the subshell does 
> *not* need to call OPAM, only obuild.
> 
> Thomas, I (think) this is what our friend in 
> https://github.com/OCamlPro/opam/issues/482 wanted :-)

I've just added to OPAM this feature.

You can now do:

$ opam config exec "obuild build" --switch= 4.01.0+mirage-xen

And this will execute 'obuild build' with the correct environment variables to 
use the compiler and tools installed in the 4.01.0+mirage-xen switch.

--
Thomas