1) done
2) steps 12,13,15 are specific to git checkout, step 14 is still necessary!
a) hyperlinked-source is not enabled by default for the boot libs and ghc source, which is AMAZING to have
b) buliding the pdf version of the user guide isn't enabled by default
c) if you have gmp lib somewhere installled in userland, ghc will by default pick that instead of doing in tree gmp, and on mac if you want to share you executables, that a no go!
d) unrelatedly, it seems that ghc build no longer includes the haddock manual in html/pdf form as it used to
3/4) i think we shouldn't make any assumptions about the path and what gcc/clang is where / shows up first, or at least that choice should be explicit :), good point on the --with-nm idea
5) i prefer not mentioning sudo ever in directions, and i actually these days install my various ghc versions into paths like ~/.install-ghc/$GHCVERSION :), and certain prefixes may or may not be locked down on recent osx it seems :)