There are some problems with our ABI list checking exposed by recent
compiler/cmake upgrades.
- For symcheck, there are typos in how XCOFF magic are defined, we
intended the second two digits to be a hex value, but our syntax doesn't
say that. Thus this will never match a valid XCOFF file.
- AIX triples can have version numbers. Those need to be discarded when
looking for an libc++ ABI list, like we do for other targets.
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