I would recommend three options, depending on how important it is for you to use the unmodified source, and your reasons for doing so.
1) LFS - short for Linux From Scratch, this un-distribution helps you build everything from original sources, making for strict adherence to your requirement. The downside is that maintenance is a formidable chore, since there is no one testing and patching for your configuration--you're the only user!
2) Gentoo - probably your best bet. You can choose your adventure, giving you the ability to do a stage 3 (installing from a bootstrapped environment, and building your system from there) , or a stage 1 (much more like LFS) but with someone doing testing and patching. The packages are darn close to mainstream.
3) Arch is also pretty close to mainstream, but slightly less so than Gentoo. Bleeding-edge sources are available with config/build packages from the community repo.
Those are really your options if you don't want to get a CS degree focused on OSes and spend your life compiling.