.build directory for cmake

[Gary Aitken]

I'm trying to port some linux code which uses cmake, and clearly don't
know what I'm doing.

I have
   USES=  cmake
set, but a
   make build
terminates with:
   cd: /usr/ports/cad/prusa-slicer/work/.build: No such file or directory

What am I missing?  I presume the .build directory should be automatically
created by the build process.

Thanks,

Gary