fix clang build with glibc 2.42 re: struct termio

[etwoo]

I hit some issues building Infer from source in my Arch Linux dev environment. The problem seems to be specific to compiling against glibc 2.42, which Arch recently accepted into its official repositories.

The fix in this PR is to backport fixes from LLVM upstream for https://github.com/llvm/llvm-project/issues/137321

• https://github.com/llvm/llvm-project/commit/59978b2
• https://github.com/llvm/llvm-project/commit/c99b1bc

[etwoo]

Assuming the feedback from https://github.com/facebook/infer/pull/1939#issuecomment-3297464996 would also apply here, I've rebased this bugfix branch onto HEAD of main.