Wrong library search path

When crosscompiling an autoconf/automake project, I pass the target's libary 
path with "LDFLAGS= -L /compiletarget/lib" as argument for the configure 
script.

But now a libtool script is created, that contains the following variable:

sys_lib_search_path_spec="/lib /usr/lib /usr/local/lib"

These paths contain of course the libraries of my workstation, incompatible 
with the crosscompile target.

During the link stage, indeed, things go wrong.
The libtool script is called, with --mode=link, and -L/compiletarget/lib, all 
object files and a library I want to link against: -ltc

Now the libtool script replaces -ltc by /usr/lib/libtc.so, it found my 
workstations version of the library, in the lib_search_path_spec.
It should have used /compiletarged/lib/libtc.so instead.
Linking fails, the library is not in a valid format for the target.

Are there any special things I need to do to tell libtool it is being used in 
a crossbuild?
Or can I influence the value of 'sys_lib_search_path_spec' that will be used?

Used versions:

autoconf 2.57
libtool 1.4.3

Regards,

Pieter