tweaking a port (build issue)

[Gary Aitken]

I'm trying to tweak a port (cad/freecad) and am having an issue getting the
build to work.

I modified a file in the /usr/ports/cad/freecad directory tree
   work/FreeCAD-0.18.4/src/Mod/Sketcher/Gui/ViewProviderSketch.cpp
and did:
   pkg deinstall
   make build
   make install
   pkg deinstall
  modify something else
   make build
     doesn't look like anything changed.

Apparently I'm using some old forgotten lore which is wrong... clues?

Thanks,

Gary