modality_keyboard: override b_lundef option to 'false'

modality_keyboard: override b_lundef option to 'false'

The modality_keyboard module is a module of mmi-manager and it'll be loaded
and used by dlopen/dlsym and some variables and apis of mmi-manager will be used
by the module. As mmi-manager is an executable, it doesn't export variables
and apis to a module. Therefore building modality_keyboard module will make
build errors like 'undefined reference to XXX'.

To not make the undefined reference errors when building modality_keyboard module,
we override b_lundef option to 'false'. Please note that the default value of
b_lundef option is 'true'.

Of cource, setting b_lundef option to 'false' will hide all the other undefined
 reference errors other than errors related to symbols of mmi-manager. Thus, we
will make mmi-manager into a share library soon. Please refer to it.

Change-Id: I7737bcec648d4f73cca81ca707534236465244b9
Signed-off-by: Sung-Jin Park <sj76.park@samsung.com>