os/dbuild.sh : fix build error
os/dbuild.sh : fix build error

In previous version, build error occured because the board name passed as an argument is changed to lowercase.
for example esp32_DevKitC is changed to esp32_devkitc.

jeongchanKim/TizenRT,Samsung/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,davidfather/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,jeongchanKim/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,sunghan-chang/TizenRT,davidfather/TizenRT,Samsung/TizenRT,pillip8282/TizenRT,chanijjani/TizenRT,Samsung/TizenRT,jeongchanKim/TizenRT,jeongarmy/TizenRT,davidfather/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,sunghan-chang/TizenRT,an4967/TizenRT,sunghan-chang/TizenRT,jsdosa/TizenRT,sunghan-chang/TizenRT,davidfather/TizenRT,jsdosa/TizenRT,jeongarmy/TizenRT,jeongarmy/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,junmin-kim/TizenRT,chanijjani/TizenRT,an4967/TizenRT,pillip8282/TizenRT,an4967/TizenRT,Samsung/TizenRT,an4967/TizenRT,chanijjani/TizenRT,an4967/TizenRT,davidfather/TizenRT,chanijjani/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,chanijjani/TizenRT,jsdosa/TizenRT,davidfather/TizenRT,jeongarmy/TizenRT,jeongchanKim/TizenRT,jsdosa/TizenRT,junmin-kim/TizenRT,chanijjani/TizenRT,davidfather/TizenRT,jeongarmy/TizenRT,chanijjani/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,sunghan-chang/TizenRT,jeongarmy/TizenRT,Samsung/TizenRT,pillip8282/TizenRT