[build2] Importing module interface partition

[Boris Kolpackov]

Sosuke Imai via users <users at build2.org> writes:

> export module egret.fundamental:concepts.integral_constant;
> import :concepts.static_value; // I want to import egret.fundamental:concepts.static_value;
> 
> With b command, I got the following error messages:
> 
> > libegret/egret/fundamental/concepts/integral_constant.mxx: error: failed to correctly guess module name from
> > libegret/:egret/fundamental/concepts/mxx{static_value}
> >   info: guessed: egret.fundamental:concepts.integral_constant:concepts.static_value
> >   info: actual:  egret.fundamental:concepts.static_value
> >   info: consider adjusting module interface file names or
> >   info: consider specifying module name with cxx.module_name

Yes, that's a bug in build2, thanks for the report. It's now fixed,
commit 274d65d2a7[1]

[1] https://git.build2.org/cgit/build2/commit/?id=274d65d2a76ed48cb618e25e0916e20ba3d5c87b