binutils: add missing dependencies for Git versions

When the binutils source code is pulled from a Git repository, a
number of generated files are not present, and need to be
re-generated. Those files are generated by flex, bison, and texinfo,
so we need to pull the corresponding dependencies.

Notice that we tried avoiding the texinfo dependency by doing a number
of MAKEINFO tricks, but none of them worked properly, so we've instead
chosen to depend on host-texinfo.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>