Stop creating stubs targets calling /usr/bin/true

It is not needed at all.

While here remove:

• the stub pre-everything:: declaration, let the framework define it if needed
• remove the stub describe target with NO_DESCRIBE is set. It is useless
• remove options-message it was only used by gnome and dropped a long time ago
• remove pre-distclean it was never used

Approved by: portmgr (mat)
Differential Revision: https://reviews.freebsd.org/D10326