Don't use FindMagnum.cmake for populating *_INSTALL_DIR variables.

It's overly complicated to hack around all find_* algorithms just to
find some dependencies and set three variables.

CMakeLists.txt

@@ -38,10 +38,19 @@ endif()
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${Magnum_SOURCE_DIR}/modules/")
 
-# Populate MAGNUM_*_INSTALL_DIR variables, check for dependencies
-set(MAGNUM_INCLUDE_DIR  "${CMAKE_CURRENT_SOURCE_DIR}/src")
-set(MAGNUM_LIBRARY      Magnum)
-include(FindMagnum)
+# Check dependencies
+find_package(Corrade REQUIRED)
+if(NOT TARGET_GLES)
+    find_package(OpenGL REQUIRED)
+    find_package(GLEW REQUIRED)
+else()
+    find_package(OpenGLES2 REQUIRED)
+endif()
+
+# Installation paths
+set(MAGNUM_LIBRARY_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/lib${LIB_SUFFIX})
+set(MAGNUM_CMAKE_MODULE_INSTALL_DIR ${CMAKE_ROOT}/Modules)
+set(MAGNUM_INCLUDE_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/include/Magnum)
 
 add_subdirectory(modules)
 add_subdirectory(src)