enable -fPIC for static build

CMakeLists.txt

@@ -139,6 +139,7 @@ else()
     add_library("${CJSON_LIB}-static" STATIC "${HEADERS}" "${SOURCES}")
     set_target_properties("${CJSON_LIB}-static" PROPERTIES OUTPUT_NAME "${CJSON_LIB}")
     set_target_properties("${CJSON_LIB}-static" PROPERTIES PREFIX "lib")
+    set_property(TARGET "${CJSON_LIB}-static" PROPERTY POSITION_INDEPENDENT_CODE ON)
 endif()
 if (NOT WIN32)
     target_link_libraries("${CJSON_LIB}" m)
@@ -181,6 +182,7 @@ if(ENABLE_CJSON_UTILS)
         target_link_libraries("${CJSON_UTILS_LIB}-static" "${CJSON_LIB}-static")
         set_target_properties("${CJSON_UTILS_LIB}-static" PROPERTIES OUTPUT_NAME "${CJSON_UTILS_LIB}")
         set_target_properties("${CJSON_UTILS_LIB}-static" PROPERTIES PREFIX "lib")
+        set_property(TARGET "${CJSON_UTILS_LIB}-static" PROPERTY POSITION_INDEPENDENT_CODE ON)
     endif()
 
     configure_file("${CMAKE_CURRENT_SOURCE_DIR}/library_config/libcjson_utils.pc.in"