[clang] ObjcRuntime.h: Add mips64, aarch64, and riscv64 to non-legacy dispatch (PR #76694)

[Hugo Melder via cfe-commits]

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@@ -101,10 +101,17 @@ class ObjCRuntime {
     // The GNUstep runtime uses a newer dispatch method by default from
     // version 1.6 onwards
     if (getKind() == GNUstep && getVersion() >= VersionTuple(1, 6)) {
-      if (Arch == llvm::Triple::arm ||
-          Arch == llvm::Triple::x86 ||
-          Arch == llvm::Triple::x86_64)
+      switch (Arch) {
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hmelder wrote:

> The version check above is not quite right for these.

This was my first approach, but it seems like GNUstep and libobjc2 unit tests are always emitting -fobjc-runtime=gnustep-2.0

So one would need to change this flag in the build configuration everytime libobjc2 gets updated.

https://github.com/llvm/llvm-project/pull/76694