vpath builds and verbose error messages

When using verbose error messages (psql \set VERBOSITY verbose) with a
vpath build, you get this sort of thing:

ERROR:  42703: column "foo" does not exist
LINE 1: select foo;              ^
LOCATION:  transformColumnRef,
/build/buildd-postgresql-9.1_9.1.1-3-i386-AP0ovQ/postgresql-9.1-9.1.1/build/../src/backend/parser/parse_expr.c:766

Can we shorten that path somehow?  Either in the C code when printing it
out, or during the build.  Any ideas?