build/tools/esp32: Modify command and operator that "dash" not support.
build/tools/esp32: Modify command and operator that "dash" not support.

In ubuntu environment, "dash" is default shell, it does not support
built-in "let" command and comparsion operator "==", so modify it
to work in both "bash" and "dash".

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