Here's a patch for Linux and also FreeBSD. The latter OS decided to
turn on ASLR by default recently, causing my workstation to fail like
this quite reliably, which reminded me to follow up with this. It
disables ASLR in pg_ctl and pg_regress, which is enough for check and
check-world, but doesn't help you if you run the server directly
(unlike the different hack done for macOS).
For whatever random reason the failures are rarer on Linux (could be
my imagination, but I think they might be clustered, I didn't look
into the recipe for the randomness), but even without reproducing a
failure it's clear to see using pmap that this has the right effect.
I didn't bother with a check for the existence of ADDR_NO_RANDOMIZE
because it's since 2.6.12 which is definitely ancient enough.
