COMP: Remove unused CMAKE_C_FLAGS for JsonCpp build.
COMP: Remove unused CMAKE_C_FLAGS for JsonCpp build.

cdeepakroy/TubeTK,aylward/ITKTubeTK,sumedhasingla/TubeTK,LucasGandel/TubeTK,KitwareMedical/ITKTubeTK,KitwareMedical/TubeTK,thewtex/TubeTK,cdeepakroy/TubeTK,cdeepakroy/TubeTK,sumedhasingla/TubeTK,LucasGandel/TubeTK,KitwareMedical/ITKTubeTK,KitwareMedical/TubeTK,sumedhasingla/TubeTK,thewtex/TubeTK,aylward/ITKTubeTK,thewtex/TubeTK,matthieuheitz/TubeTK,cdeepakroy/TubeTK,matthieuheitz/TubeTK,matthieuheitz/TubeTK,KitwareMedical/ITKTubeTK,LucasGandel/TubeTK,aylward/ITKTubeTK,LucasGandel/TubeTK,KitwareMedical/TubeTK,aylward/ITKTubeTK,sumedhasingla/TubeTK,matthieuheitz/TubeTK,KitwareMedical/TubeTK,KitwareMedical/ITKTubeTK,thewtex/TubeTK