build: Move all of lp under LPR option

[des]

Summary

• Tag related directories with package=lp

• Make the examples/printing directory conditional on MK_LPR

• Make the hosts.lpd(5) manual page conditional on MK_LPR

MFC after: 1 week

[ziaee]

lpr and lpd are mentioned in hier(7), should we do something with that in this commit?

[des]

In D55408#1267241, @ziaee wrote:

lpr and lpd are mentioned in hier(7), should we do something with that in this commit?

Not until we actually remove the code.

[des]

more tags

[des]

missed a directory

[des]

examples/printing was listed twice

[des]

more concise

[ivy]

the reason you get an empty lp package is that package=lp in mtree causes the directory to be unconditionally installed, so what you actually have is a package containing only that directory. we don't have a good solution to this right now; i think the right fix is that we would simply not build packages that only contain directories, but i haven't had a chance to look at this recently...

for previous cases, the workaround has been to not tag directories which are arch-specific or depend on src.conf knobs.

[ivy]

D55412

[des]

Tested in combination with D55408 and D55380. oops, wrong review