[Buildroot] RFC: add check for post-build script existence?

[Danomi Manchego]

Thomas,

> I'm not sure where you're getting ${BOARD_NAME} from, but why don't you
> handle the board differences in the script itself?

I forgot all about adding an "export" before the makefile variable
could also get passed to the bash script itself.  (To be honest, I
only recently learned that there actually *was* a makefile export
command.)  That's good enough for me.

Thanks for the prompt response and good advice.

Danomi -