[CIR][CodeGen] Aggregate constructor with non-constant size

[tommymcm]

Minimal test case:

struct A {
  A() {}
};
int foo() {
  int b;
  new A[b];
}

Assertion:

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

Line 1853 in aeac352

llvm_unreachable("NYI");