games/chessx: Improve port
- After remove ".if ${COMPILER_TYPE} == clang":
- remove ".include <bsd.port.pre.mk>";
- replace ".include <bsd.port.post.mk>" with ".include <bsd.port.mk>".
- Remove the useless block from the patch that adds one blank line.
PR: 292841
Approved by: Alexey Vyskubov <alexey@pentode.fi> (maintainer, timeout 2 weeks)