Find the correct install paths for systemd units and udev rules (#2046)

cmake/FindUdev.cmake

@@ -0,0 +1,28 @@
+# - Try to find Udev
+# Once done this will define
+#
+# UDEV_FOUND - system has udev
+# UDEV_RULES_INSTALL_DIR - the udev rules install directory
+
+IF (NOT WIN32)
+
+    find_package(PkgConfig QUIET)
+    if(PKG_CONFIG_FOUND)
+        pkg_check_modules(UDEV "udev")
+    endif()
+
+    if (UDEV_FOUND)
+        execute_process(COMMAND ${PKG_CONFIG_EXECUTABLE}
+            --variable=udevdir udev
+            OUTPUT_VARIABLE UDEV_RULES_INSTALL_DIR)
+
+        string(REGEX REPLACE "[ \t\n]+" "" UDEV_RULES_INSTALL_DIR
+            "${UDEV_RULES_INSTALL_DIR}")
+
+        set(UDEV_RULES_INSTALL_DIR "${UDEV_RULES_INSTALL_DIR}/rules.d")
+
+        mark_as_advanced(UDEV_RULES_INSTALL_DIR)
+
+    endif ()
+
+ENDIF ()