While here, sort ONLY_FOR_ARCHS as recommended by portlint.
Approved by: robak (mentor)
Test Plan
$ pwd
/usr/ports/www/node6
$ portlint -C
WARN: Makefile: [0]: possible direct use of command "python" found. use ${PYTHON_CMD} instead.
WARN: Makefile: possible use of absolute pathname "/etc/make.conf".
0 fatal errors and 2 warnings found.