1. Declare UNIX98 PTY requirement in host system requirements and check
it in the script. All desktop or server distros should have it now,
but let's stop anyone from building on a embedded distro w/o UNIX98
PTY early...
2. Use Expect test suite as a guard against mishandled $LFS/dev/pts.
3. No need to test the basic function of Expect in Binutils anymore
because if ($LFS)/dev/pts is not good, the Expect test suite would
have failed.