Update for building

This PR updates the binutils/gcc built for sparc as a cross compiler to build using the gcc built for native use. It requires /opt/pl-build-tools/i386/bin/i386-pc-solaris2.11-gcc to have already been built. 

This also updates the toolchain file to take a variable for prefix, so we can update that file as little as possible.

Also, cmake wasn't installing, which was throwing a wrench into the build process.

Rahul, let me know if anything here needs changing or updating. 
I wasn't sure if we should put a dependency on i386 gcc having already been built for this. What do you think?