install the desktop files on OpenBSD too

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -324,7 +324,7 @@ install(DIRECTORY resources
         )
 
 # Install desktop shortcuts for Linux
-if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+if ((${CMAKE_SYSTEM_NAME} MATCHES "Linux") OR (${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD"))
     message("Installing desktop files")
 
     # Install icons