install ODBC driver components if only flex was found

cmake/install.inc

@@ -20,16 +20,20 @@ ELSEIF (TD_WINDOWS)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.lib DESTINATION driver)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.exp DESTINATION driver)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.dll DESTINATION driver)
+  if(FLEX_FOUND)
     INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/todbc.lib DESTINATION driver)
     INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/todbc.exp DESTINATION driver)
     INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/todbc.dll DESTINATION driver)
+  endif ()
 
   IF (TD_POWER)
     INSTALL(FILES ${EXECUTABLE_OUTPUT_PATH}/power.exe DESTINATION .)
   ELSE ()
     INSTALL(FILES ${EXECUTABLE_OUTPUT_PATH}/taos.exe DESTINATION .)
     INSTALL(FILES ${EXECUTABLE_OUTPUT_PATH}/taosdemo.exe DESTINATION .)
+    if(FLEX_FOUND)
       INSTALL(FILES ${EXECUTABLE_OUTPUT_PATH}/todbcinst.exe DESTINATION .)
+    endif ()
   ENDIF ()
 
   #INSTALL(TARGETS taos RUNTIME DESTINATION driver)