[CIR][CodeGen][Builtin] `longjmp` handling

[tommymcm]

Minimized test case:

A() { __builtin_longjmp(A, 1); }

Failed assertion:

clangir/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

Line 1847 in aeac352

llvm_unreachable("BI__builtin_longjmp NYI");