xbps-src: document -Q non-recursiveness

[tornaria]

Document in usage that running check with -Q is not recursive,
and running check with -K is recursive.

This behaviour was implemented in #54633.

Testing the changes

• I tested the changes in this PR: YES|briefly|NO

[classabbyamp]

recursive might be a bit obtuse, what about specifying it as "and run tests on built dependencies" or something?

[tornaria]

recursive might be a bit obtuse, what about specifying it as "and run tests on built dependencies" or something?

I'd call that "concise" but point taken. What about:

-Q  Enable running the check stage (for the target package only).

-K  Enable running the check stage with longer tests (and also on built deps).

I'm trying to stick on one 80 char line, spelling "dependencies" brings the line to 86 char.
With two lines:

-Q  Enable running the check stage, for the target package only.

-K  Enable running the check stage with longer tests.
    Unlike -Q, this will also run the check stage on built dependencies.

[ahesford]

I favor the second option. Better to be verbose and break a line.

[tornaria]

A few days later, I now agree verbose is better, and using two lines looks better.