Add USES=pathfix support for CMake. Some ports that use CMake to build
already had USES=pathfix, although it did nothing. For those ports, I
either removed it as they were handling the pkgconfig files differently
or I removed patches and substitutions that accomplished the same thing
as pathfix.

Differential Revision: https://reviews.freebsd.org/D850
Reviewed by: antoine, bapt, tijl
Approved by: portmgr (bapt)