Take built in json if available

FSL/CMakeLists.txt

@@ -14,7 +14,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
 find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)
-find_package(nlohmann_json REQUIRED)
+#find_package(nlohmann_json REQUIRED)
 
 
 
@@ -27,9 +27,14 @@ set(PROJECT_SOURCES ${sources} ${headers}  ${uis} )
 add_executable(fsl ${PROJECT_SOURCES} )
 
 target_link_libraries(fsl PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)
-target_link_libraries(fsl PRIVATE nlohmann_json::nlohmann_json)
 
 
+if( GEOMODEL_USE_BUILTIN_JSON )
+   add_dependencies( GXClashPointSystems JSONExt )
+else()
+   target_link_libraries(fsl PRIVATE nlohmann_json::nlohmann_json)
+endif()
+
 # Install the executable.
 install( TARGETS fsl
    EXPORT ${PROJECT_NAME}-export