"make -j4 world" falls over

I ran into $SUBJECT whilst doing trial RPM packaging of 9.1.  The problem
is that make starts building contrib modules before errcodes.h has been
made, leading to failures such as

In file included from ../../src/include/postgres.h:48:0,                from auth_delay.c:12:
../../src/include/utils/elog.h:69:28: fatal error: utils/errcodes.h: No such file or directory
compilation terminated.
In file included from ../../src/include/postgres.h:48:0,                from adminpack.c:15:
../../src/include/utils/elog.h:69:28: fatal error: utils/errcodes.h: No such file or directory
compilation terminated.

I can work around this for the moment, but I think it's a "must fix"
before release.
        regards, tom lane