title: uEnv.txt file not generated when compiling uboot
body: <p>I'm working on U-Boot for the embedded board(NXP).
  When I compile U-Boot; the uEnv.txt file is not created after the build. Does anyone know what configuration OR some change in Uboot source code I have to change in uboot for generating uEnv.txt after the build? If it's a change in the uboot source code then please suggest patch for the same.
  If you suggest some beginner-friendly documentation then it would be a great help.</p>