[proposal][FMV] Make target_clones and target_version mixable

[DanielKristofKiss]

as proposed llvm/llvm-project#74358 (comment) here let's make possible to mix target_clones with target_version.

__attribute__((target_clones("dotprod", "aes"))) 
int callee(void) {
    return 42;
}

__attribute__((target_version("default"))) 
int callee(void) {
    return 0;
}

int caller(void) {
    return callee();
}

[vhscampos]

Hi, thanks for your issue report.

If possible, we encourage you to contribute with a Pull Request that addresses this issue. We will be happy to review it.

[labrinea]

I have created #310 for this.