* lib/open.c (open): When have_cloexec is still undecided, do pass a
O_CLOEXEC flag to orig_open.
* lib/openat.c (rpl_openat): When have_cloexec is still undecided, do
pass a O_CLOEXEC flag to orig_openat.
* tests/test-open.h (test_open): Verify that O_CLOEXEC is honoured.
* modules/open-tests (Depends-on): Add fcntl.
* modules/openat-tests (Depends-on): Likewise.
* modules/fcntl-safer-tests (Depends-on): Likewise.