Crash with label in block

[ChuanqiXu9]

Reproducer:

// repro.c
struct Struct {};
struct Struct get_struct ();
void do_something (struct Struct);
void test (int cand)
{
  {
    label:
      do_something(get_struct());
  }
}

Compile it with clang -fclangir -c repro.c we can get:

loc("repro.c":8:5): error: must be the first operation in a block
fatal error: error in backend: CIR codegen: module verification error before running CIR passes

[bcardosolopes]

cc: @gitoleg