Add terminating newlines to output files

[jamesreprise]

The POSIX definition of a line requires that it is terminated with a newline. https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_206

A new function spit-file has been added to rules-clojure.fs which wraps spit, adding a new line the content spat into files if it lacks one.

We use this function whenever want to write files to disk.

[SevereOverfl0w]

Why would content not end in a newline already?

[jamesreprise]

spit doesn't automatically suffix with a newline when creating a file. Git's native diff and GitHub confirm this problem:

 filegroup(name = "__clj_files",
        srcs = ["....clj"],
-       data = ["..."])
\ No newline at end of file
+       data = ["..."])

Note the red symbol at the bottom of the file signifying a lack of a newline.

In an 'offline' discussion we discussed alternate approaches involving changes to emit-bazel to ensure that Bazel DSL always ends in a newline.