[Boost-build] OS X build patch

Subject: [Boost-build] OS X build patch
From: Phillip Seaver (phil_at_[hidden])
Date: 2013-11-19 14:49:47

I've finally updated our copy of boost-build (from 2 years ago), and I'm
very glad I did.  The speed difference on startup is huge.  Thanks for
continuing to support and improve this.

I ran into a couple of problems when building on OS X 10.8 with Xcode 5
that I have solutions for in the attached patch.

The first was that one of my files wouldn't compile when an included
header #error'ed because SSE instructions weren't enabled.  MacPorts
found the problem and worked around it a different way.  Based on their
comments, I changed the -march argument to be "prescott" if no
instruction set is specified. 
https://trac.macports.org/ticket/35172#comment:15

The second was that Xcode puts the SDK's in a different place now, so I
added that directory to the search list.

There are also some compiler warnings when building bjam.  I can send
them to whoever is interested.

Phillip