(cmake) use FetchContent cmake module to retrieve jsoncpp third party dependency

ixbots/CMakeLists.txt

@@ -31,11 +31,6 @@ add_library(ixbots STATIC
     ${IXBOTS_HEADERS}
 )
 
-find_package(JsonCpp)
-if (NOT JSONCPP_FOUND)
-  set(JSONCPP_INCLUDE_DIRS ../third_party/jsoncpp)
-endif()
-
 if (USE_PYTHON)
   target_compile_definitions(ixbots PUBLIC IXBOTS_USE_PYTHON)
   find_package(Python COMPONENTS Development)
@@ -48,12 +43,11 @@ set(IXBOTS_INCLUDE_DIRS
     ../ixwebsocket
     ../ixcobra
     ../ixredis
-    ../ixsentry
-    ${JSONCPP_INCLUDE_DIRS}
-    ${SPDLOG_INCLUDE_DIRS})
+    ../ixsentry)
 
 if (USE_PYTHON)
   set(IXBOTS_INCLUDE_DIRS ${IXBOTS_INCLUDE_DIRS} ${Python_INCLUDE_DIRS})
 endif()
 
 target_include_directories( ixbots PUBLIC ${IXBOTS_INCLUDE_DIRS} )
+target_link_libraries( ixbots jsoncpp_static )