Fix another typo.

contrib/zlib/CMakeLists.txt

@@ -198,7 +198,7 @@ endif(MINGW)
 
 add_library(zlibstatic STATIC ${ZLIB_SRCS} ${ZLIB_ASMS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
 
-IF(WIN32
+IF(WIN32)
     INSTALL( TARGETS zlibstatic
              EXPORT "${TARGETS_EXPORT_NAME}"
              LIBRARY DESTINATION ${ASSIMP_LIB_INSTALL_DIR}