First pass at super project build.

CMakeLists.txt

@@ -1,10 +1,21 @@
 cmake_minimum_required(VERSION 3.5)
 
-project(jwp-mosquitto-plugin)
+# https://github.com/Sarcasm/cmake-superbuild/
+option (USE_SUPERBUILD "Whether or not a superbuild should be invoked" ON)
 
-add_subdirectory(ext/jwt-cpp)
+if (USE_SUPERBUILD)
+  project(jwp-mosquitto-plugin-super)
+  include(external-deps.cmake)
+  return()
+else()
+  project(jwp-mosquitto-plugin)
+endif()
+
+find_package(jwt-cpp)
+find_package(OpenSSL)
 
 add_library(jwp-plugin SHARED src/jwp-plugin.cpp)
 
 add_executable(jwt-example src/jwt-example.cpp)
-target_link_libraries(jwt-example PRIVATE jwt-cpp)
+target_include_directories(jwt-example PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/jwt-cpp/include)
+target_link_libraries(jwt-example OpenSSL::Crypto)

external-deps.cmake

@@ -0,0 +1,26 @@
+include (ExternalProject)
+
+set (DEPENDENCIES)
+set (EXTRA_CMAKE_ARGS)
+
+list(APPEND DEPENDENCIES ep_jwt-cpp)
+ExternalProject_Add(ep_jwt-cpp
+  PREFIX ep_jwt-cpp
+  GIT_REPOSITORY "https://github.com/Thalhammer/jwt-cpp.git"
+  GIT_TAG "v0.5.2"
+  GIT_SHALLOW "True"
+  CMAKE_ARGS -DJWT_CMAKE_FILES_INSTALL_DIR=${CMAKE_CURRENT_BINARY_DIR}/jwt-cpp -DCMAKE_INSTALL_PREFIX=${CMAKE_CURRENT_BINARY_DIR}/jwt-cpp
+  BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/jwt-cpp
+)
+list (APPEND EXTRA_CMAKE_ARGS
+  -Djwt-cpp_DIR=${CMAKE_CURRENT_BINARY_DIR}/jwt-cpp
+)
+
+ExternalProject_Add (ep_jwp-mosquitto-plugin
+  PREFIX ep_jwp-mosquitto-plugin
+  DEPENDS ${DEPENDENCIES}
+  SOURCE_DIR "${PROJECT_SOURCE_DIR}"
+  CMAKE_ARGS -DUSE_SUPERBUILD=OFF ${EXTRA_CMAKE_ARGS}
+  INSTALL_COMMAND ""
+  BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}
+)