Carlo Marcelo Arenas Belón [off-list ref] writes:
Platforms that are using the git compatibility layer for unsetenv
use void as a return value for unsetenv(), so any function that checks
for a return value will fail to build.
It sounds like barking up a wrong tree. unsetenv() is supposed to
signal success with 0 and failure with -1, and the compat/
implementation is broken, not the caller that tries to be nice and
check the error return from the system function it calls.
Not that adding the unused wrapper, and leaving it unused, was a
wise decision in hindsight, though.