Undefined symbol in Clang-compiled Python extension using OpenMP - clang

Question

I am facing a weird problem when compiling a Python extension featuring OpenMP with Clang.
Minimal Example
I managed to boil down my actual problem to the following code:
The Python extension could not be much simpler, while still featuring OpenMP.
Apart from the function bar, this is mostly standard boilerplate:
# include <Python.h>
static PyObject * bar(PyObject *self)
{
#pragma omp parallel sections
{
#pragma omp section
{float x=42.0; x+=1;}
}
Py_RETURN_NONE;
}
static PyMethodDef foo_methods[] = {
{"bar", (PyCFunction) bar, METH_NOARGS, NULL},
{NULL, NULL, 0, NULL}
};
static struct PyModuleDef moduledef = {
PyModuleDef_HEAD_INIT, "foo", NULL, -1,
foo_methods, NULL, NULL, NULL, NULL
};
PyMODINIT_FUNC PyInit_foo(void)
{
return PyModule_Create(&moduledef);
}
With the above being foo.c, I compile and load this with:
clang -fPIC -fopenmp -I/usr/include/python3.7m -c foo.c -o foo.o
clang -shared foo.o -o foo.so -lgomp
python3 -c "import foo"
The last line, i.e., the import of the module throws the following error:
ImportError: /home/wrzlprmft/…/foo.so: undefined symbol: __kmpc_for_static_fini
What I found out so far
This does not happen when replacing Clang with GCC.
This does not happen with regular shared libraries (not involving Python).
Using Setuptools to compile the extension does not help.
(In fact, my compile commands are a reduction of what Setuptools does to find out whether it uses any non-essential compiler extensions that cause this.)
All of this happens on Ubuntu 19.10 with Python 3.7, Clang 9.0.0-2, and GCC 9.2.1.
I can also replicate the problem on current Arch Linux with Python 3.8 and Clang 9.0.1.
This worked until a year ago, probably longer.
Using Python 3.6 does not help.
Using Clang 3.8, 4.0, 6.0, 7, or 8 does not help.
Here, somebody reports a similar problem when trying to compile TensorFlow.
This is yet unsolved.
Question
What is going wrong here and how can I fix this?
Right now I do not even have an idea whether this is an error by me, in Clang, OpenMP, or Python.