[llvm] [SystemZ] Serialize ada entry flags (PR #169395)

[Ulrich Weigand via llvm-commits]

https://github.com/uweigand commented:

Hmm.  My one concern with this is that we chose overlapping value ranges for the MO_ flags used for Linux and z/OS.  This patch applies the z/OS mapping everywhere, which I guess could lead to broken results on Linux?  We might have to distinguish the two cases here.  (Or else untangle the value ranges?  Not sure what's better.)

https://github.com/llvm/llvm-project/pull/169395