Duplicate symbol in Clang (but not GCC) when overriding __cxa_throw

Question

I'm trying to get a bit more information in __cxa_throw. Regardless of the wisdom of this, the following code works perfectly with gcc and from the limited information I can find about this, it should work its perfectly legal even if there are some caveats. Please note I'm only planning this for debug builds. Clang is giving

ld.lld: error: duplicate symbol: __cxa_throw
>>> defined at exc_override.cpp
>>>            exc.o:(__cxa_throw)
>>> defined at cxa_exception.cpp
>>>            cxa_exception.cpp.o:(.text.__cxa_throw+0x0) in archive /opt/compilers/clang-12.0.1/bin/../lib/x86_64-unknown-linux-gnu/c++/libc++.a

main.cxx

#include <iostream>
#include <stdexcept>
#include "exc_override.h"

int main(int argc, char** argn) {

    try {
        throw std::runtime_error("boom");
    } catch(...)
    {
        std::cout << "caught" << std::endl;
    }

    return 0;
}

exc_override.h

#pragma once

extern "C"
void __cxa_throw (void *thrown_exception, void *pvtinfo, void (*dest)(void *)) ;

exc_override.cpp

#include "exc_override.h"
#include <cstdlib>
#include <dlfcn.h>
#include <execinfo.h>
#include "stdio.h"

typedef void (*cxa_throw_type)(void *, void *, void (*) (void *));
cxa_throw_type orig_cxa_throw = 0;

void load_orig_throw_code()
{
    orig_cxa_throw = (cxa_throw_type) dlsym(RTLD_NEXT, "__cxa_throw");
}

extern "C"
void __cxa_throw (void *thrown_exception, void *pvtinfo, void (*dest)(void *)) {
    printf(" ################ DETECT A THROWN !!!!! #############\n");
    if (orig_cxa_throw == 0)
        load_orig_throw_code();
    
    {}
    orig_cxa_throw(thrown_exception, pvtinfo, dest);
}

and I'm building it in gcc (4.8.5) with the following commands

gcc main.o exc_override.o -o testprogram
g++ main.o exc_override.o -o testprogram
g++ main.o exc_override.o -o testprogram -ldl >

In Clang 12.0.1

clang++ -c main.cxx -o main.o
clang++ -c exc_override.cpp -o exc.o
clang++ main.o exc.o -o testprogram