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

[m.ostapenko at samsung dot com]

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

--- Comment #6 from Maxim Ostapenko <m.ostapenko at samsung dot com> ---
Created attachment 40007
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40007&action=edit
Untested fix.

Attaching untested fix.
Dominique, could you try it?