Two fixes for script(1): 1. Don't do tty stuff to stdin if stdin isn't a tty. 2. When running in non-interactive mode, don't select(2) on the standard input.
Two fixes for script(1):
1. Don't do tty stuff to stdin if stdin isn't a tty.
2. When running in non-interactive mode, don't select(2)
on the standard input.

This un-breaks non-interactive portupgrade.

PR: bin/59036 [1]
PR: bin/56166, bin/57414, ports/57415, ports/60534 [2]
MFC after: 7 days
Approved by: rwatson (mentor)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase