is not familiar to me. Is it created along with your cross toolchain? If not, I don't think the compiler will look for it in it's sysroot directory tree (and it does sound like your toolchain was built with a sysroot). You can try setting environment variables like CC, CFLAGS, LDFLAGS, etc to specify where the compiler & linker should look for headers, libraries, etc. These can also be specified on the commandline, or you can edit the Makefile to do this.
LDFLAGS='-L /some/special/library/location' make
make LDFLAGS+='-L /some/special/library/location'