The LIT test cases were migrated with the script provided by
Nikita Popov.
No manual changes were made. Committed without review since
no functional changes, after consultation with uweigand.
In order to build the Linux kernel, the back chain must be supported with
packed-stack. The back chain is then stored topmost in the register save
area.
Review: Ulrich Weigand
Differential Revision: https://reviews.llvm.org/D74506