makechrootpkg: Prevent collecting coredumps

Coredumps from build chroots are not generally useful. Prevent
them from being generated.

Avoids a lot of annoyance from the GCC testsuite spawning lots of
systemd-coredump processes.

Just set the soft limit so the user can still raise it in the PKGBUILD
if they insist.

makechrootpkg.in

@@ -241,8 +241,12 @@ EOF
 # These functions aren't run in makechrootpkg,
 # so no global variables
 _chrootbuild() {
+	# No coredumps
+	ulimit -c 0
+
 	# shellcheck source=/dev/null
 	. /etc/profile
+
 	# Beware, there are some stupid arbitrary rules on how you can
 	# use "$" in arguments to commands with "sudo -i".  ${foo} or
 	# ${1} is OK, but $foo or $1 isn't.