[Bug sanitizer/78267] [7 Regression] libsanitizer breaks bootstrap on x86_64-apple-darwin16 at r241977

[howarth.at.gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78267

--- Comment #9 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
(In reply to Maxim Ostapenko from comment #6)
> Created attachment 40007 [details]
> Untested fix.
> 
> Attaching untested fix.
> Dominique, could you try it?

The change fixes the bootstrap of current gcc trunk here on
x86_64-apple-darwiin15 against Xcode 8.2 beta.