package/efl/libefl: add harfbuzz dependency

Harfbuzz allow to enable complex text shaping and layouting support in
efl libraries.

Also, it one of the "highly recommended" dependencies according to the
README but disabling it doesn't need the
--enable-i-really-know-what-i-am-doing... option.  That's why harfbuzz
is not added to BR2_PACKAGE_LIBEFL_HAS_RECOMMENDED_CONFIG.

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>