Backporting glibc-2.31 fixes to llvm-8.0.1 and llvm-9.0.1 series

Him

Recently, glibc 2.31 broke the sanitizers-common build due to an ABI
change. A fix for the same has been provided at

https://reviews.llvm.org/rG947f9692440836dcb8d88b74b69dd379d85974ce

I was wondering if there is interest in backporting the fix to llvm
8.0.1 and llvm 9.0.1 series.

I have applied the patch and resolved the minor conflicts for the same
at these two branches which can be applied directly on top of the
current branches:
https://github.com/jayeshbadwaik/llvm-project/tree/llvmorg-8.0.1-glibc-fix
https://github.com/jayeshbadwaik/llvm-project/tree/llvmorg-9.0.1-glibc-fix

I have successfully built and tested llvm with the two branches.

Thank you.