PrintAsClang is supposed to emit declarations in the same order regardless of the compiler’s internal state, but we have repeatedly found that our current criteria are inadequate, resulting in non-functionality-affecting changes to generated header content. Add a diagnostic that’s emitted when this happens soliciting a bug report.
Since there *should* be no cases where the compiler fails to order declarations, this diagnostic is never actually emitted. Instead, we test this change by enabling `-verify` on nearly all PrintAsClang tests to make sure they are unaffected.
This did demonstrate a missing criterion that only mattered in C++ mode: extensions that varied only in their generic signature were not sorted stably. Add a sort criterion for this.
In LLVM unified builds `%swift_obj_root` points to `<LLVM build dir>/tools/swift`,
and folders like `bin`, `lib` and `share` are not under `swift_obj_root`, which
makes some tests fail.
For the cases in which `%swift_obj_root/lib` was used, replace it by
using `%swift-lib-dir` instead. Replicate `%swift-lib-dir` to create
`%swift-bin-dir` and `%swift-share-dir`, and use those instead of
`%swift_obj_root/bin` and `%swift_obj_root/share`.
This alternates work both in Swift build-script builds and also in LLVM
unified builds.
