[clang] [analyzer] Fix crash analyzing _BitInt() in evalIntegralCast (PR #66782)

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https://github.com/DonatNagyE approved this pull request.

This commit was reverted once (see discussion on earlier pull request  #65887), because the buildbot linaro-clang-armv8-quick couldn't handle the large `_BitInt()`s in the testcase. Pinning to the x86_64 triple solves this problem, so it's safe to resubmit the commit now.

https://github.com/llvm/llvm-project/pull/66782