The VM should provide you with two compilers: gcc (which will compile binaries for x86), and arm-linux-gcc (which will compile ARM binaries). You just need to specify this compiler as the one your system uses. I'm not using the VM to build stuff but I assume that it has arm-linux-gcc in the PATH environment variable (echo $PATH ... look for /usr/local/DigiEL-5.9/x-tools/arm-[stuff]-linux-gnueabi/bin). If that's the case, for a generic autoconf-based library (I'll use lzo as an example), you can do this:
tar -xvzf lzo-2.06.tar.gz
CFLAGS='your favorite cflags' ./configure --build=x86_64-unknown-linux-gnu --host=arm-linux --target=arm-linux
... using --build, --host, and --target will tell the autoconf script that arm-linux-gcc is your compiler and it will figure the rest out on its own.
If your open source library doesn't use autoconf, you'll have to do other stuff like setting CC=arm-linux-gcc but that's going to vary based on what the build process is.
When you're done compiling, you can verify that the final product will run on the module by finding an executable and checking its type; in the lzo example I would say
and the output will look something like this:
testmini: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.16, not stripped