[Sparc] Remove the support for builtin setjmp/longjmp

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 four 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.

Reviewers: jyknight, joerg, venkatra

Subscribers: fedor.sergeev, jrtc27, llvm-commits

Differential Revision: https://reviews.llvm.org/D51487

llvm-svn: 343210