Improve the fix for PR64242.  Various optimizations can change a memory
reference into a frame access.  Given there are multiple virtual frame pointers
which may be replaced by multiple hard frame pointers, there are no checks for
writes to the various frame pointers.  So updates to a frame pointer tends to
generate incorrect code.  Improve the previous fix to also add clobbers of
several frame pointers and add a scheduling barrier.  This should work in most
cases until GCC supports a generic "don't optimize across this instruction"
feature.

Bootstrap OK. Testcase passes on AArch64 and x86-64.  Inspected x86, Arm,
Thumb-1 and Thumb-2 assembler which looks correct. 

    gcc/
	PR middle-end/64242
	* builtins.c (expand_builtin_longjmp): Add frame clobbers and schedule
	block.
	(expand_builtin_nonlocal_goto): Likewise.

    testsuite/
	PR middle-end/64242
	* gcc.c-torture/execute/pr64242.c: Update test.

From-SVN: r271870