[Toaster] [review-request] bbarrosp/build-button

[Barros Pena, Belen]

Came across an issue with the 'new build' form today: the 'build' button
was enabled after project selection, and whenever a valid project was
selected. This meant you could start a build without specifying a target.

I have a patch in

http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/log/?h=bbarrosp/buil
d-button

2170b42c53ca58aa3aa787f63e136bfac4a13ddc

Disable build button as needed

Thanks!

Belén