builtins: use NORETURN macro
builtins: use NORETURN macro

Now that we have the NORETURN macro, use that to mark the function as noreturn,
rather than the GNU __attribute__.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@249985 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt