makefile: stop setting unused HGEXTDIR variable during osx build...
makefile: stop setting unused HGEXTDIR variable during osx build
The variable was added in
a38ed42cd23c (osx: include chg by default,
2017-03-20), but I can't find any others references to the variable in
that commit or in any other commits.
Differential Revision:
https://phab.mercurial-scm.org/D8915