Repeated pg_upgrade buildfarm failures on binturon

Hi,

Binturon has repeatedly failed with errors like:
ERROR:  could not open file "base/16400/32052": No such file or directory

E.g.
http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=binturong&dt=2015-07-06%2014%3A20%3A24

It's not just master that's failing, even older branches report odd
errors:
connection to database failed: FATAL:  could not open relation mapping file "global/pg_filenode.map": No such file or
directory
http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=binturong&dt=2015-07-06%2014%3A53%3A10

Greetings,

Andres Freund