PR #145685 introduced constructor overload ambiguity in the Triple
class, causing `updateTripleOSVersion()` to construct Triple objects
with `unknown` instead of the configured target triple (e.g.,
`powerpc-ibm-aix7.3.0.0`). This results in Clang driver errors like
`error: unknown target triple 'unknown'`.
Used `Twine` constructor with braced initialization to bypass ambiguity.
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Co-authored-by: Tony Varghese <tony.varghese@ibm.com>
Co-authored-by: Matt Arsenault <arsenm2@gmail.com>
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