add basic cmake support

cmake/Modules/FindSystemd.cmake

@@ -0,0 +1,23 @@
+#######
+# Find systemd service dir
+# sets variables
+# SYSTEMD_FOUND
+# SYSTEMD_SERVICES_INSTALL_DIR
+if (NOT SYSTEMD_FOUND)
+    pkg_check_modules(SYSTEMD "systemd")
+endif(NOT SYSTEMD_FOUND)
+
+if (SYSTEMD_FOUND AND "${SYSTEMD_SERVICES_INSTALL_DIR}" STREQUAL "")
+    execute_process(COMMAND ${PKG_CONFIG_EXECUTABLE}
+        --variable=systemdsystemunitdir systemd
+        OUTPUT_VARIABLE SYSTEMD_SERVICES_INSTALL_DIR)
+    string(REGEX REPLACE "[ \t\n]+" "" SYSTEMD_SERVICES_INSTALL_DIR
+        "${SYSTEMD_SERVICES_INSTALL_DIR}")
+elseif (NOT SYSTEMD_FOUND AND SYSTEMD_SERVICES_INSTALL_DIR)
+    message (FATAL_ERROR "Variable SYSTEMD_SERVICES_INSTALL_DIR is\
+        defined, but we can't find systemd using pkg-config")
+endif()
+
+if (SYSTEMD_FOUND)
+    message(STATUS "systemd services install dir: ${SYSTEMD_SERVICES_INSTALL_DIR}")
+endif(SYSTEMD_FOUND)