gcc: Linewrap configure options

No changes, just linewrapping for easier reading such that one option
goes on each line.  This will make it easier to see what changes in
diffs between book edits, plus it's easier to read in the rendered book,
too.
createbuilddir: Make a sysroot dir

So we can keep cross compiler and created libs separate from the final
system.
binutils: Wrap configure options

No other changes.
binutils: Remove --prefix, use new sysroot dir
gcc: Remove AR=ar and LDFLAGS from gcc builds

They aren't needed with gmp, mpfr, and mpc in tree and there are no host
libs built for embedded.