machine or vendor specific execution of a function

I've run into this construct a few times with my work in upgrading the customers older dunfell Yocto system to Scarthgap in recipes:

do_compile:append:<some specific string specifier>(){
....
}

It appears to very problematic both in functions and variable value definitions. What is that string specifier? In the case I'm running into it is set to "qoriq" usually. But in a few examples in the vendor's code I see it set to "qoriq-ppc". Which is correct? From a high level both are correct but neither will give the desire approach. Since locally we are only building for one platform I can just remove it and this will work for my situation.

Where is this value being set and how do I find out which one I want? There is no machine called "qoriq" or "qoriq-ppc". There is a MACHINE variable (in my case t1024rdb-64b) but setting it to that doesn't work either.

Cheers!!