> One example is 'srcdir': this value is only useful in the build tree and 
> there currently is no clean way to signal that you are retrieving a 
> value that is not useful.

In the particular case of 'srcdir', sysconfig.is_python_build() tells you whether the value is useful.

Concerns about sysconfig often returning values which are meaningless for the current configuration can be discussed in another issue.

Unless there are objections I will close.