Build::warnings() provides an option to set whether warnings are desired.

Calling Build::warnings(true) will pass in -Wall or a platform equivalent, however, counterintuitively, calling Build::warnings(false) will not pass a -w or a platform equivalent.

Either the option should be fixed to behave intuitively, or replaced with another intuitively-behaving method -- one that would actually suppress the warnings when called with false as an argument.