modules: populate ${MAGNUM_LIBRARIES} before they are used.

MAGNUM_LIBRARIES are used in all Application classes. I don't know when
this got broken, but now it is fixed again.

modules/FindMagnum.cmake

@@ -162,12 +162,22 @@ if(NOT _TARGET_DESKTOP_GLES EQUAL -1)
     set(MAGNUM_TARGET_DESKTOP_GLES 1)
 endif()
 
+# Dependent libraries and includes
+set(MAGNUM_INCLUDE_DIRS ${MAGNUM_INCLUDE_DIR}
+    ${MAGNUM_INCLUDE_DIR}/MagnumExternal/OpenGL
+    ${CORRADE_INCLUDE_DIR})
+set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARY}
+    ${CORRADE_UTILITY_LIBRARIES}
+    ${CORRADE_PLUGINMANAGER_LIBRARIES})
 if(NOT MAGNUM_TARGET_GLES OR MAGNUM_TARGET_DESKTOP_GLES)
     find_package(OpenGL REQUIRED)
+    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGL_gl_LIBRARY})
 elseif(MAGNUM_TARGET_GLES2)
     find_package(OpenGLES2 REQUIRED)
+    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGLES2_LIBRARY})
 elseif(MAGNUM_TARGET_GLES3)
     find_package(OpenGLES3 REQUIRED)
+    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGLES3_LIBRARY})
 endif()
 
 # On Windows and in static builds, *Application libraries need to have
@@ -359,21 +369,6 @@ find_package_handle_standard_args(Magnum
     REQUIRED_VARS MAGNUM_LIBRARY MAGNUM_INCLUDE_DIR
     HANDLE_COMPONENTS)
 
-# Dependent libraries and includes
-set(MAGNUM_INCLUDE_DIRS ${MAGNUM_INCLUDE_DIR}
-    ${MAGNUM_INCLUDE_DIR}/MagnumExternal/OpenGL
-    ${CORRADE_INCLUDE_DIR})
-set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARY}
-    ${CORRADE_UTILITY_LIBRARIES}
-    ${CORRADE_PLUGINMANAGER_LIBRARIES})
-if(NOT MAGNUM_TARGET_GLES OR MAGNUM_TARGET_DESKTOP_GLES)
-    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGL_gl_LIBRARY})
-elseif(MAGNUM_TARGET_GLES2)
-    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGLES2_LIBRARY})
-else()
-    set(MAGNUM_LIBRARIES ${MAGNUM_LIBRARIES} ${OPENGLES3_LIBRARY})
-endif()
-
 # Installation dirs
 include(CorradeLibSuffix)
 set(MAGNUM_LIBRARY_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/lib${LIB_SUFFIX})