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. 
Since the only change between i386 and sparc is in the environment, why not set that as a variable such that
```
binutilenv=$(if $(filter sparc,$(arch)),PATH=.. CC=.. CXX=...,)
```
and use it like
```
(cd $(@D) && env $(binutilenv) $(rootdir)/source/$(binutils_)/configure
```