cmake: add FindSYSTEMD module

Fixes: https://github.com/transmission/transmission/issues/117

CMakeLists.txt

@@ -373,9 +373,7 @@ endif()
 
 if(WITH_SYSTEMD)
     tr_get_required_flag(WITH_SYSTEMD SYSTEMD_IS_REQUIRED)
-
-    pkg_check_modules(SYSTEMD ${SYSTEMD_IS_REQUIRED} libsystemd)
-
+    find_package(SYSTEMD)
     tr_fixup_auto_option(WITH_SYSTEMD SYSTEMD_FOUND SYSTEMD_IS_REQUIRED)
 endif()
 

cmake/FindSYSTEMD.cmake

@@ -0,0 +1,20 @@
+if(UNIX)
+    find_package(PkgConfig QUIET)
+    pkg_check_modules(PC_SYSTEMD QUIET libsystemd)
+endif()
+
+find_path(SYSTEMD_INCLUDE_DIR NAMES systemd/sd-daemon.h HINTS ${PC_SYSTEMD_INCLUDE_DIRS})
+find_library(SYSTEMD_LIBRARY NAMES systemd HINTS ${PC_SYSTEMD_LIBRARY_DIRS})
+
+include(FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args(SYSTEMD
+    REQUIRED_VARS
+        SYSTEMD_LIBRARY
+        SYSTEMD_INCLUDE_DIR
+)
+
+mark_as_advanced(SYSTEMD_INCLUDE_DIR SYSTEMD_LIBRARY)
+
+set(SYSTEMD_INCLUDE_DIRS ${SYSTEMD_INCLUDE_DIR})
+set(SYSTEMD_LIBRARIES ${SYSTEMD_LIBRARY})

daemon/CMakeLists.txt

@@ -36,17 +36,16 @@ add_executable(${TR_NAME}-daemon
     ${${PROJECT_NAME}_HEADERS}
     ${${PROJECT_NAME}_WIN32_RC_FILE})
 
-set_target_properties(${TR_NAME}-daemon PROPERTIES
-    COMPILE_FLAGS "${SYSTEMD_CFLAGS}"
-    LINK_FLAGS "${SYSTEMD_LDFLAGS}"
-)
-
 target_link_libraries(${TR_NAME}-daemon
     ${TR_NAME}
     ${EVENT2_LIBRARIES}
-    ${SYSTEMD_LIBRARIES}
 )
 
+if(WITH_SYSTEMD)
+    target_include_directories(${TR_NAME}-daemon PRIVATE ${SYSTEMD_INCLUDE_DIRS})
+    target_link_libraries(${TR_NAME}-daemon ${SYSTEMD_LIBRARIES})
+endif()
+
 tr_win32_app_info(${PROJECT_NAME}_remote_WIN32_RC_FILE
     "Transmission Utility ('remote')"
     "${TR_NAME}-remote"