Allow __attribute__((swift_attr)) in attribute push pragmas

This change allows SwiftAttr to be used with #pragma clang attribute push
to add Swift attributes to large regions of header files.
We plan to use this to annotate headers with concurrency information.

Patch by: Becca Royal-Gordon

Differential Revision: https://reviews.llvm.org/D112773

GitOrigin-RevId: 290cddcd139d668251821f11426f37481faf6d7f
3 files changed