buildroot

cjson: build shared and static library

cjson 1.6.0 added the BUILD_SHARED_AND_STATIC_LIBS option which is OFF
by default so set it depending on BR2_SHARED_STATIC_LIBS value.

If BUILD_SHARED_AND_STATIC_LIBS is set to OFF, cjson uses the standard
BUILD_SHARED_LIBS option which is passed by the cmake-package
infrastructure.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>