cmake: Set BUILDING_URBI_SDK.
cmake: Set BUILDING_URBI_SDK.

Change-Id: Id1e2614c87ea09a895c594d3b98cd53b389a6e83

urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi