Override statements

Prefixing a variable assignment with the override keyword prevents that variable's value from ever being changed again, except by way of another override statement. This is functionality that Starlark doesn't support.

It can be removed by checking if the variable is defined before reassigning it. For example, replace:

override MY_VAR := foo
MY_VAR := bar
# MY_VAR is foo here

with:

MY_VAR := foo

# Generally this would be in a separate file that is included
ifndef MY_VAR
MY_VAR := bar
enddef

# MY_VAR is foo here