This reverts commit 0dbc0067604eb9629d1458fcf2b226a88e728f14, reversing
changes made to cb7f7742652acdf3086b3d132163b5ea2c2328eb.
Should go into staging.
Factor a bintools (i.e. binutils / cctools) wrapper out of cc-wrapper. While
only LD is wrapped, the setup hook defines environment variables on behalf of
other utilites.