[Bug target/90835] Incompatibilities with macOS 10.15 headers

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90835
Bug 90835 depends on bug 66970, which changed state.

Bug 66970 Summary: Add __has_builtin() macro
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66970

           What    |Removed                     |Added
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             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED