FindDlopen.cmake: Don't run the FindDlopen module more than once.

extras/buildsystem/cmake/include/FindDlopen.cmake

@@ -8,12 +8,15 @@
 # Copyright (c) 2007 Erik Johansson <erik@ejohansson.se>
 # Redistribution and use is allowed according to the terms of the BSD license.
 
-include(CheckLibraryExists)
 
 # Assume dlopen is not found.
-set(Dlopen_FOUND FALSE)
+if (Dlopen_SEARCHED)
+    include(CheckLibraryExists)
 
-foreach (library c c_r dl)
+    set(Dlopen_SEARCHED TRUE)
+    set(Dlopen_FOUND FALSE)
+
+    foreach (library c c_r dl)
       if (NOT Dlopen_FOUND)
         check_library_exists(${library} dlopen "" Dlopen_IN_${library})
 
@@ -23,16 +26,17 @@ foreach (library c c_r dl)
         endif (Dlopen_IN_${library})
 
       endif (NOT Dlopen_FOUND)
-endforeach (library)
+    endforeach (library)
 
-if (Dlopen_FOUND)
+    if (Dlopen_FOUND)
       if (NOT Dlopen_FIND_QUIETLY)
         message(STATUS "Found dlopen in: ${Dlopen_LIBRARIES}")
       endif (NOT Dlopen_FIND_QUIETLY)
-else (Dlopen_FOUND)
+    else (Dlopen_FOUND)
       if (Dlopen_FIND_REQUIRED)
         message(FATAL_ERROR "Could not find the library containing dlopen")
       endif (Dlopen_FIND_REQUIRED)
-endif (Dlopen_FOUND)
+    endif (Dlopen_FOUND)
 
-mark_as_advanced(Dlopen_LIBRARIES)
+    mark_as_advanced(Dlopen_LIBRARIES)
+endif(Dlopen_SEARCHED)
\ No newline at end of file