[clang] [compiler-rt] [libcxx] [cmake] Add hexagon-linux cmake cache files (PR #98712)

[Louis Dionne via llvm-commits]

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ldionne wrote:

Meta comment: As part of our support policy, we would like to have a CI job that builds and tests libc++ for Hexagon. I'm not very familiar with that target, but do you think you could set that up?

https://github.com/llvm/llvm-project/pull/98712