When ObjectFileMachO reads a Mach-O file for a 32-bit arm cpu,

set the triple's "vendor" field to Apple.  

We don't want to assume a vendor of Apple for all Mach-O files -
this breaks x86_64 EFI debugging where they put non-Apple binaries
in a Mach-O format for ease of handling.

But on armv7, Apple's ABI always uses r7 as the frame pointer
register; if we don't set the Vendor field to Apple, we can pick
up a generic armv7 ABI where the fp is r11 (or r7 for thumb) which
breaks backtracing altogether.

Greg is reluctant for us to make any assumptions about the Vendor
here, but we'll see how this shakes out.  It's such a big problem
on armv7 if we don't know this is using the Apple ABI that it's worth
trying this approach.

<rdar://problem/22137561> 

llvm-svn: 258387