[Sparc] Remove the support for builtin setjmp/longjmp

[dcederman]

Summary

It is currently broken and for Sparc there is not much benefit in using a builtin version compared to a library version. Both versions needs to store the same 4 values in setjmp and flush the register windows in longjmp. If the need for a builtin setjmp/longjmp arises there is an improved implementation available at https://reviews.llvm.org/D50969.

[jyknight]

LGTM. :)