The __chkstk function can be at a greater than 4 GiB offset from our
generated function. Fix derived from https://reviews.llvm.org/D7267

Change-Id: Ife87dcd42541676828c4a0ca77dcded6649ce278
Reviewed-on: https://swiftshader-review.googlesource.com/8932Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>