Doesn't look like it causes any failures in the full test suite, so
presumably it's fine!

Patch from Stephen Blackheath

Apparently ios doesn't understand .type %function.

They're both the same register, and Linux seems happy with both,
but ios only accepts r11.

Apparently ios only understands .globl, but Linux appears to understand
both.

Based on patch from Stephen Blackheath.

We now use the 'host' to determine whether stage0 builds terminfo,
and 'target' to determine whether stage1 does.

We don't build it if the platform is either Windows or ios.

This makes the build system a little simpler, and in particular
will make it easier to handle the changes needed for cross-compilation.

[ ] is m4 syntax, so we need to use 'test foo' rather than '[ foo ]'.

It's now only used once

pipeLoop now returns the final dflags, rather than having
runPipeline' extract it from the end state.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>