tools: remove unused pkgsrc directory

The pkgsrc Makefile target was removed in 2015

Refs: https://github.com/nodejs/node/pull/1938

PR-URL: https://github.com/nodejs/node/pull/28783


Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>