fix invalid endif statement in cmake.

CMakeLists.txt

@@ -521,7 +521,7 @@ SET ( ASSIMP_BUILD_ARCHITECTURE "" CACHE STRING
 IF( ASSIMP_BUILD_ARCHITECTURE STREQUAL "")
 ELSE()
   ADD_DEFINITIONS ( -D'ASSIMP_BUILD_ARCHITECTURE="${ASSIMP_BUILD_ARCHITECTURE}"' )
-ENDIF())
+ENDIF()
 
 # ${CMAKE_GENERATOR}
 SET ( ASSIMP_BUILD_COMPILER "" CACHE STRING