smoothing Xcode integration

[Uxio Prego]

Hi,
if you happen to use GNU Bison from Apple Xcode, I got a
question for you:

How would you detect Xcode from GNU Make?

I would want to run `sed 's/#line/\/\/#line/'` on the generated parser
in order for it not to show as assembly during debugging. I think
Xcode has some kind of non honoring to the way `#line` works, I
mean I think GDB is working as it seems it is meant to, when I
debug the same software on Debian GNU/Linux.

Can't just simply use `uname -s` detection of `Darwin` because a
Homebrew only toolchain is to be maintained in parallel to the
Xcode project configuration docs. It has to specifically detect
Xcode somehow.

My Xcode right now is reported as `Version 9.0 (9A235)`.

I just asked StackOverflow:
https://stackoverflow.com/questions/52672051/

Thanks in advance,