pgsql: Make archiver's SIGQUIT handler exit via _exit().

Make archiver's SIGQUIT handler exit via _exit().

Commit 8e19a8264 changed the SIGQUIT handlers of almost all server
processes not to run atexit callbacks. The archiver process was
skipped, perhaps because it's not connected to shared memory; but
it's just as true here that running atexit callbacks in a signal
handler is unsafe. So let's make it work like the rest.

In HEAD and v13, we can use the common SignalHandlerForCrashExit
handler. Before that, just tweak pgarch_exit to use _exit(2)
explicitly.

Like the previous commit, back-patch to all supported branches.

Kyotaro Horiguchi, back-patching by me

Discussion: /messages/by-id/1850884.1599601164@sss.pgh.pa.us

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/67dde49a3ddb263cee5b8fadbd8519302f603392

Modified Files
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src/backend/postmaster/pgarch.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)