package/vlc: add optional support for minizip

package/vlc: add optional support for minizip

When minizip was compiled before, vlc will use it as optional
dependency:

$ output/host/usr/bin/x86_64-linux-readelf -a output/target/usr/lib/vlc/plugins/access/libzip_plugin.so | grep NEEDED | sort
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libdl.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libintl.so.8]
 0x0000000000000001 (NEEDED)             Shared library: [libminizip.so.1]
[...]

The build system offers no option to en-/disable minizip support,
the same is valid for zlib support:
https://git.videolan.org/?p=vlc.git;a=blob;f=configure.ac;h=be658816bcda642090e1cff20d93e61b25299250;hb=HEAD#l831

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>