Incorrect apt-util-1.pc using --with-expat=builtin

[Rhys Ulerich]

I've noticed atop APR Utils 1.5.3 that when I configure using
--with-expat=builtin I see the following within the installed
${prefix}/lib/pkgconfig/apr-util-1.pc:
    Libs: -L${libdir} -laprutil-${APRUTIL_MAJOR_VERSION}
/g/g10/ulerich1/Build/apr-util-1.5.3/xml/expat/libexpat.la
while I'd expect to see
    Libs: -L${libdir} -laprutil-${APRUTIL_MAJOR_VERSION}  -lexpat
as the former build directory isn't guaranteed to exist after the
installation and ${prefix}/lib/libexpat.la and friends are installed
correctly.

A workaround is manually stitching up the installed pkg-config file.

Thanks,
Rhys