cmake: Add option to build dlib submodule

Fedora provides package `dlib` and `dlib-devel` so that it is
unnecessary to build dlib.

CMakeLists.txt

@@ -9,6 +9,7 @@ set(PLUGIN_URL "https://obsproject.com/forum/resources/face-tracker.1294/")
 set(LINUX_MAINTAINER_EMAIL "[email protected]")
 
 option(WITH_PTZ_TCP "Enable to connect PTZ camera through TCP socket" ON)
+option(WITH_DLIB_SUBMODULE "Link dlib from submodule" ON)
 option(ENABLE_MONITOR_USER "Enable monitor source for user" OFF)
 option(ENABLE_DEBUG_DATA "Enable property to save error and control data" OFF)
 option(WITH_DOCK "Enable dock" ON)
@@ -36,16 +37,18 @@ find_package(obs-frontend-api REQUIRED)
 include(cmake/ObsPluginHelpers.cmake)
 find_qt(VERSION ${QT_VERSION} COMPONENTS Widgets Core Gui)
 
-set(CMAKE_POSITION_INDEPENDENT_CODE True)
-set(DLIB_NO_GUI_SUPPORT ON)
-set(DLIB_PNG_SUPPORT OFF)
-set(DLIB_GIF_SUPPORT OFF)
-set(DLIB_USE_FFMPEG OFF)
-set(DLIB_JPEG_SUPPORT OFF)
-set(DLIB_LINK_WITH_SQLITE3 OFF)
-set(DLIB_WEBP_SUPPORT OFF)
-set(DLIB_TEST_COMPILE_ALL_SOURCE_CPP OFF)
-add_subdirectory(dlib)
+if (WITH_DLIB_SUBMODULE)
+	set(CMAKE_POSITION_INDEPENDENT_CODE True)
+	set(DLIB_NO_GUI_SUPPORT ON)
+	set(DLIB_PNG_SUPPORT OFF)
+	set(DLIB_GIF_SUPPORT OFF)
+	set(DLIB_USE_FFMPEG OFF)
+	set(DLIB_JPEG_SUPPORT OFF)
+	set(DLIB_LINK_WITH_SQLITE3 OFF)
+	set(DLIB_WEBP_SUPPORT OFF)
+	set(DLIB_TEST_COMPILE_ALL_SOURCE_CPP OFF)
+	add_subdirectory(dlib)
+endif()
 
 set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)