I don't see any reason for waitid.c not be be built with
-fasynchronous-unwind-tables when other files such as wait.c and waitpid.c
use -fasynchronous-unwind-tables. This patch adds that option and thereby
fixes nptl/tst-cancelx4 and ntpl/tst-cancelx5 for MIPS (O32), where they
previously failed with the cleanup handlers for waitid not being run.