> Can you look inside config.log and see what did configure find when it
> ran this fragment?  Here it says this:
>
>   configure:8755: checking whether make supports nested variables
>   configure:8772: result: yes

I don't have that in my config.log, just

am_cv_make_support_nested_variables=yes

(that's the only reference to nested variables in all of config.log)

>   configure:3820: checking for GNU Make
>   configure:3870: result: make