This is a good stop-gap, it allows a user to manually take control of the situation, without impacting the current default behavior.

I presume that a more robust solution would likely employ the output of the compiler to determine what's the target, but that's more work and more risk, which can be attempted later.

As a side note, UNAME is a variable, so it can already be taken over by the user,
but I guess it's also used in several other places, and you only want to impact this one place.

Exactly, the UNAME variable is also used to select different tools depending on what OS you are running on, like here:

Thanks for the PR @RicBent!