Using clang version 20.1.2

clang++ -target "mipsel-w64-windows-gnu" -c test.cpp

[[__noreturn__]] inline void g() {
  __builtin_unreachable();
}

void f(int i)
{
  if (i == 0)
    g();
}

Note that using clang instead of clang++ doesn't exhibit the problem.
Possible workaround: add -O3