cmake: Use pkg-config instead for json-c dev package.

src/modules/nsq/CMakeLists.txt

@@ -4,13 +4,19 @@ add_library(${module_name} SHARED ${MODULE_SOURCES})
 
 find_package(Libev REQUIRED)
 
-find_package(json-c QUIET)
-if(NOT json-c_FOUND)
-  message(STATUS "json-c not found. looking with pkg-config")
-  find_package(PkgConfig REQUIRED)
-  pkg_check_modules(json-c REQUIRED IMPORTED_TARGET json-c)
-  add_library(json-c::json-c ALIAS PkgConfig::json-c)
-endif()
+# TODO: When we have a proper cmake config file for json-c for most OS, we can
+# use that instead of pkg-config.
+# json-c v 0.14 and 0.15 have wrong include directories in their cmake config
+# files. uncomment the following line when we have a proper cmake config file
+# for json-c for most OS.
+# find_package(json-c 0.16 CONFIG)
+
+# if(NOT json-c_FOUND)
+# message(STATUS "json-c not found. looking with pkg-config")
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(json-c REQUIRED IMPORTED_TARGET json-c)
+add_library(json-c::json-c ALIAS PkgConfig::json-c)
+# endif()
 
 find_package(CURL REQUIRED)