build: set ENABLE_IPC to OFF when fuzzing

Currently a `BUILD_FOR_FUZZING` build will failure to configure, with
missing `capnp`.

Author: fanquake

CMakeLists.txt

@@ -217,6 +217,7 @@ if(BUILD_FOR_FUZZING)
   set(BUILD_TESTS OFF)
   set(BUILD_GUI_TESTS OFF)
   set(BUILD_BENCH OFF)
+  set(ENABLE_IPC OFF)
   set(BUILD_FUZZ_BINARY ON)
 
   target_compile_definitions(core_interface INTERFACE