Leo P. Singer authored Feb 16, 2017 and Adam Mercer committed Feb 18, 2017

select() will always return immediately for a FIFO because reads
will never block. As a result, this loop was busy-waiting.
There is no easy way to portably read past EOF on a FIFO on stdin
without busy-waiting. The usual trick to avoid EOF on a FIFO is
to open the FIFO for both reading and writing. As long as at least
one writer is open, no EOF will occur. Unfortunately, we cannot
use this trick here because we cannot open stdin for writing.
Fixes #5153.
(cherry picked from commit 4a491b97563f0bc8f057da307cb01f477974279c)
Original: 7bdc32153eedfa210332dd99f3f129372f16e807