[clang][OpenMP] Fix bug #62099 - use hash value when inode ID cannot be determined (#131646)
When creating the name of an outlined region, Clang uses the file's
inode ID to generate a unique name. When the file does not exist, this
causes a fatal abort of the compiler. This PR switches to a has value
that is used instead.
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Co-authored-by: Michael Kruse <github@meinersbur.de>