Typically, for other sorts of build configuration data, we have relied on extracting that from the ./configure-produced Makefile and making it available via sysconfig.get_config_var().  I think we should be cautious about bloating sys.implementation with platform-specific data unless there is an overriding need for it, for example, if it is needed during interpreter initialization before sysconfig can be initialized.  If not, I'd look at adding the needed values as configuration variables in configure.ac.