[clang] [SystemZ][z/OS] This change adds support for the PPA2 section in zOS (PR #65407)

[Fangrui Song via cfe-commits]

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@@ -33,13 +33,33 @@ namespace sys {
 template <typename D = std::chrono::nanoseconds>
 using TimePoint = std::chrono::time_point<std::chrono::system_clock, D>;
 
+// utc_clock and utc_time are only available since C++20. Add enough code to
+// support formatting date/time in UTC.
+class UtcClock : public std::chrono::system_clock {};
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MaskRay wrote:

This Support change needs to be split from this patch with a unittest in llvm/unittest/Support.

Many people will think this z/OS patch is unrelated to them.

https://github.com/llvm/llvm-project/pull/65407