defaults.t: Android needs some %ENV variables to remain

Technically this isn't Android specific, but android
requires it because of two tangentially related
issues:

    * $^X on android currently returns 'perl',
      rather than a full path. So $ENV{PATH} is needed.
    * perls built with -Duseshrplib need to be able to
      find their libperl.so, but Android's linker will
      only look in /system/lib, which is a read-only
      filesystem and thus unlikely to have the
      user-supplied libperl. This means that
      $ENV{LD_LIBRARY_PATH} is needed.