vpath builds and include paths

[jling]

I was doing a test where I am using GNU automake and autoconf.  I have 
a directory structure such as:

/test
     Makefile.am
     configure.in

/test/project1
     Makefile.am

/test/project1/sublevel
     Makefile.am

/test/project1/sublevel/src
     myproj.cpp
     Makefile.am

/test/project1/sublevel/inc
     myproj.hpp


The contents of /test/project1/sublevel/src/Makefile.am is:

     INCLUDE = -I../inc
     lib_LIBRARIES = libmyproj.a
     libmyproj_a_SOURCES = myproj.cpp myproj.hpp

So this works alright if I am building within the source tree (i.e. 
myproj.a is built in /test/project1/sublevel/src).

However, if I want to build in a separate build tree (relying on 
VPATH), then I try the following:

mkdir /build
cd /build
/test/configure
make

This attempts to build in this new /build directory, but during 
compilation it cannot locate the header file, myproj.hpp, and the rest 
of the build fails.  What do I need to do in order to tell automake 
where this header is?  I've already tried using the absolute path 
variables in the Makefile.am:

INCLUDE = -I$(abs_top_srcdir)/project2/sublevel/inc

This doesn't seem to help.

Thanks,
John