functions: fixes for add_binary on non-binary files

functions: always return 0 early when a non-binary file is passed to add_binary

138374f0 added a condition to add_binary that if the non-binary file does not have a shebang, the function returns successfully before trying to parse sodeps. Before the change, the function returned in all cases when the file was not a binary.

Bring back the previous behaviour of returning early on non-binaries.

Fixes 138374f0

functions: call the non-binary files with shebangs a "script"

Calling them binaries is not correct. They could be called executables, but since we do not enforce the execute (+x) permissions on the added files, it would be wrong too. Since they have shebangs, they are scripts, so let's call them that.