get-rusage-as, pthread_sigmask tests: Fix -fsanitize=thread findings. * lib/get-rusage-as.c (get_rusage_as): When compiled by "gcc -fsanitize=thread", don't try get_rusage_as_via_setrlimit. * tests/test-pthread_sigmask2.c (main): Clean up the killer_thread before exiting.

#define __xstrtol xstrtoumax
#define __strtol_t uintmax_t
#define __spec PRIuMAX
#include "test-xstrtol.c"