Update to the latest att/ast commit on github.
This brings in the following important commit on github:
Ensure fd 0, 1, 2 are never closed Closing stdin, stdout, or stderr is extremely dangerous and should never be done. If an attempt is made to do so redirect the file descriptor to /dev/null. Similarly, if ksh is started with one of those fd's closed open it on /dev/null before doing anything else. Resolving upstream issue #1117.