[Bug target/67710] FAIL: gcc.dg/darwin-*version-*.c (test for excess errors) with Xcode 7

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67710

--- Comment #6 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Iain Sandoe from comment #5)
> (In reply to ro@CeBiTec.Uni-Bielefeld.DE from comment #4)
> > Unfortunately, it doesn't work on Mac OS X 10.11.2: every link test
> > FAILs with
> > 
> > FAIL: 17_intro/freestanding.cc (test for excess errors)
> > Excess errors:
> > ld: warning: object file
> > (/var/folders/1d/k16rgv6d5039jhvlj8_dzk4h00021y/T//cc0iIoOX.o) was built for
> > newer OSX version (10.11.2) than being linked (10.11)
> > 
> > I've found that while ld strips the micro version passed to
> > -mmacosx_version_min, clang does not, resulting in this mess.
> 
> hum.
> >  Given that ld(1) documents the version number format as <major>.<minor>, for
> > now it seems that gcc should only pass this to as and ld.
> 
> ld < 85.2..ish didn't understand the minor.
>  
> > Looking...

So i've drafted a patch that pushes -asm_macosx_version_min=10.xx as a
driver-only option and started to test it out as an add-on to your patch.

Unfortunately, proving that the assembler accepts -mmacosx-version-min= ..
doesn't prove that it ends up in the object.

xc-7.2 (10.10, 11) does
xc-6.2 (10.9) accepts -mmacosx-version-min= (with -q to invoke the llvm
assembler) but the load command is not emitted.
xc-5.1.1 (10.8) as per xc-6.2

.. right now I don't know if this is significant (except to my back-ported
ld64-253.3)

testing a patch, will post here when it's baked.