The zlib support is a must if you are using RPM backend. So this
explicitly enable it and adds a comment in the recipe to avoid its
removal by mistake.
(From OE-Core rev: 7d056397ab9912316064db850aae05aacabc726c)
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>