[Bug bootstrap/89864] [9 regression] gcc fails to build/bootstrap with XCode 10.2

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89864

--- Comment #43 from Iain Sandoe <iains at gcc dot gnu.org> ---
Created attachment 46110
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46110&action=edit
Proof-of-principle path

Does this work for you?
 - my local testing says it generates the right wrapped include file.

(perhaps the constraint on darwin version was too tight in Erik's case)