annoying pkg-config problem on 64 bit Ubuntu 8.10

[Dan Kegel]

On Ubuntu 8.10:

$ pkg-config --libs dbus-1
-L//lib -ldbus-1

This leads to

configure:13190: checking for dbus_connection_close in -ldbus-1
configure:13225: gcc -m32 -o conftest -g -O2
-DDBUS_API_SUBJECT_TO_CHANGE -I/usr/include/hal
-I/usr/include/dbus-1.0 -I/usr/lib/dbus-1.0/include    conftest.c
-ldbus-1 -L//lib -lhal -ldbus-1    >&5
/usr/bin/ld: //lib/libdbus-1.so: incompatible target
configure:13253: result: no

Also affects sane.

Haven't checked Jaunty yet to see if it's still busted.
We may need to postprocess pkg-config's output to add the missing 32
in some cases.  Not sure if it's worth it.