[llvm] [SystemZ][z/OS] Move emission of PPA1 (PR #208543)

[Ulrich Weigand via llvm-commits]

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@@ -71,11 +72,42 @@ class SystemZTargetStreamer : public MCTargetStreamer {
   virtual void emitADA(MCSymbol *Sym, MCSection *Section) {}
 };
 
-class SystemZTargetGOFFStreamer : public SystemZTargetStreamer {
+class SystemZzOSStreamer : public SystemZTargetStreamer {
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uweigand wrote:

I think it does make sense to introduce this intermediate layer in the object hierarchy.  However, for naming consistency it should be called `SystemZTargetzOSStreamer`, I think.

Also, it would be good then to move the declarations of the z/OS specific methods (`emitADA` etc.) into this new class rather than the `SystemZTargetStreamer` base class, so they cannot be used by accident in Linux code.

https://github.com/llvm/llvm-project/pull/208543