glib/tests/gdatetime.c: Fix TZ envvar test on Windows
glib/tests/gdatetime.c: Fix TZ envvar test on Windows

Windows does not recognize the "America/Recife" as a valid timezone
identifier, so setting the TZ envvar to that will result in "UTC" to
be returned on Windows.

Instead, set TZ to be the Windows equivilant "SA Eastern Standard
Time", and see whether that is indeed our identifier when we create the
GTimeZone using that.

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib