Add sh_binary[_host] for shell script that should be installed as executable

We've been putting these in cc_prebuilt_binary, but that's not really
correct. It also tries adding '.exe' to the end of windows executables,
which isn't desirable for bat files.

Test: Use sh_binary_host
Change-Id: Idd5418dceb81ac55b766c987fbb69a810aeb8a3b