libewf - fix download link

Closes #20913.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
denominator 2.1.0

Closes #20946.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
libstfl: Don't build against ruby 2.0+

Fixes mistydemeo/tigerbrew#83.