Fix compilation error when USB CDC on Boot is enabled (#2080) #755

Job	Run time
Gen_Matrix	4s
Build_Example (.)	2m 53s
Build_Example (./examples/IRServer)	2m 31s
Build_Example (./examples/DumbIRRepeater)	2m 16s
Build_Example (./examples/IRsendDemo)	2m 18s
Build_Example (./examples/SmartIRRepeater)	3m 23s
Build_Example (./examples/CommonAcControl)	2m 49s
Build_Example (./examples/IRrecvDumpV3)	11m 52s
Build_Example (./examples/TurnOnFujitsuAC)	1m 16s
Build_Example (./examples/TurnOnPanasonicAC)	1m 23s
Build_Example (./examples/ControlSamsungAC)	3m 56s
Build_Example (./examples/IRrecvDumpV2)	10m 38s
Build_Example (./examples/TurnOnToshibaAC)	1m 15s
Build_Example (./examples/IRGCTCPServer)	2m 33s
Build_Example (./examples/IRrecvDemo)	2m 23s
Build_Example (./examples/LGACSend)	2m 15s
Build_Example (./examples/IRMQTTServer)	6m 50s
Build_Example (./examples/TurnOnGreeAC)	1m 22s
Build_Example (./examples/IRsendProntoDemo)	2m 21s
Build_Example (./examples/Web-AC-control)	1m 33s
Build_Example (./examples/TurnOnDaikinAC)	1m 19s
Build_Example (./examples/TurnOnMitsubishiAC)	1m 21s
Build_Example (./examples/BlynkIrRemote)	2m 29s
Build_Example (./examples/TurnOnTrotecAC)	1m 17s
Build_Example (./examples/TurnOnKelvinatorAC)	1m 16s
Build_Example (./examples/JVCPanasonicSendDemo)	2m 11s
Build_Example (./examples/TurnOnMitsubishiHeavyAc)	1m 35s
Build_Example (./examples/IRrecvDump)	2m 22s
Build_Example (./examples/IRGCSendDemo)	2m 18s
Build_Example (./examples/TurnOnArgoAC)	2m 12s
Build_Examples	1s
	1h 24m 12s

Provide feedback