[travis] add library size report support (#4239)
[travis] add library size report support (#4239)


openthread/openthread,srickardti/openthread,bukepo/openthread,jwhui/openthread,lanyuwen/openthread,chshu/openthread,bukepo/openthread,chshu/openthread,chshu/openthread,librasungirl/openthread,chshu/openthread,chshu/openthread,openthread/openthread,openthread/openthread,librasungirl/openthread,srickardti/openthread,jwhui/openthread,librasungirl/openthread,lanyuwen/openthread,lanyuwen/openthread,srickardti/openthread,abtink/openthread,bukepo/openthread,jwhui/openthread,abtink/openthread,abtink/openthread,librasungirl/openthread,jwhui/openthread,chshu/openthread,abtink/openthread,openthread/openthread,srickardti/openthread,lanyuwen/openthread,lanyuwen/openthread,bukepo/openthread,lanyuwen/openthread