I tested executing the command against one of our sample apps and it worked fine. The issue was only reproduced when I placed an .exe file in the apps folder. Basically, this is unsupported file type (as well as .bat file type) and AppBuilder
will not build the app if such is presented.
Would you check the contents of the app's folder and remove the executable file if there is such. In case, this is not the reason for the error and it still occurs on your side, may I ask you to share the project you are deploying? That way I will test it locally and advice further.