[llvm] [z/OS] Add z/OS archive reading support (PR #187110)

[zhijian lin via llvm-commits]

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+## Test reading a z/OS archive.
+
+# RUN: llvm-ar t %p/Inputs/zos-archive-test.a | FileCheck %s --check-prefix=LIST
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diggerlin wrote:

I think we need to test to extra the member file from the zos-archive-test.a , and compare the content of the extra member file is correct or not ?

https://github.com/llvm/llvm-project/pull/187110