(cmake) Stop using FetchContent cmake module to retrieve jsoncpp third party dependency

ixbots/CMakeLists.txt

@@ -31,6 +31,11 @@ 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)
@@ -43,11 +48,12 @@ set(IXBOTS_INCLUDE_DIRS
     ../ixwebsocket
     ../ixcobra
     ../ixredis
-    ../ixsentry)
+    ../ixsentry
+    ${JSONCPP_INCLUDE_DIRS}
+    ${SPDLOG_INCLUDE_DIRS})
 
 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 )