Following the warnings on building the test module:
#7491 (comment)

This PR addresses it:

• by defining _XOPEN_SOURCE with a value of 700 ( nanosleep only needs _POSIX_C_SOURCE >= 199309L ) but I believe there is arm on using a more recent macro:

Defining _XOPEN_SOURCE with a value of 700 or greater produces
the same effects as defining _POSIX_C_SOURCE with a value of
200809L or greater. Where one sees _POSIX_C_SOURCE >= 200809L

• Removing the unused variable.