move rc_svcdir to /run/openrc on Linux systems

If you are not using linux, this should not affect you.

If you are using linux, from this point forward, openrc requires the
/run directory to be a mounted tmpfs. If it is, you can run
@LIBEXECDIR@/sh/migrate-to-run.sh as root to migrate your dependency
tree and state information to the new location. If it is not, you must
create the /run directory as root with permissions 755 then reboot your
system.

reported-by: Maxim Kammerer <mk@dee.su>
X-Gentoo-Bug: 401059
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=401059

sh/.gitignore

@@ -10,3 +10,4 @@ ifwatchd-carrier.sh
 ifwatchd-nocarrier.sh
 udhcpc-hook.sh
 tmpfiles.sh
+migrate-to-run.sh