glibc: Add missing binutils dependency

glibc: Add missing binutils dependency

glibc has it's dependencies handled more manually due to it's place
in the toolchain bootstrap. It depends upon the compiler and indirectly
through that to binutils. This did mean that if binutils changes and the
compiler does not, sstate and hash equivalence could mean that glibc
wouldn't rebuild.

Add a direct dependency on binutils that if it changes, it forces glibc
to rebuild, as it should.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>