Make fftw and tcl-tk recommended dependencies.
Make fftw and tcl-tk recommended dependencies.

Allows to optionally disable some dependencies which are difficult to build on older versions of MacOS, and are not crucial to the core operation of grass.

[ci skip]

OSGeo/homebrew-osgeo4mac,OSGeo/homebrew-osgeo4mac,OSGeo/homebrew-osgeo4mac