Crash if there is no newline at the end of the file on Linux

Hi,
We use sourceKitten in the following way: sourcekitten doc --spm-module <ourModule>" and everything is fine.
But if there is a *.swift file without a newline at the end of the file we get the following error:

/usr/lib/ruby/2.3.0/json/common.rb:156:in `initialize': A JSON text must at least contain two octets! (JSON::ParserError)
	from /usr/lib/ruby/2.3.0/json/common.rb:156:in `new'
	from /usr/lib/ruby/2.3.0/json/common.rb:156:in `parse'
	from /var/lib/gems/2.3.0/gems/jazzy-0.9.3/lib/jazzy/sourcekitten.rb:794:in `parse'
	from /var/lib/gems/2.3.0/gems/jazzy-0.9.3/lib/jazzy/doc_builder.rb:145:in `build_docs_for_sourcekitten_output'
	from /var/lib/gems/2.3.0/gems/jazzy-0.9.3/lib/jazzy/doc_builder.rb:77:in `build'
	from /var/lib/gems/2.3.0/gems/jazzy-0.9.3/bin/jazzy:15:in `<top (required)>'
	from /usr/local/bin/jazzy:23:in `load'
	from /usr/local/bin/jazzy:23:in `<main>'

But only on linux (we use the container norionomura/jazzy:0.9.3_swift-4.1.2 to build it on linux)
(This happens to us, because some developers in our team don't use Xcode, which adds always a newline at the end of the file)

Reproduce sourcekitten doc --spm-module <yourModule> on Linux with a Swift file that lacks a final newline, then inspect the generated output alongside the JSON parsing failure shown in the stack trace. Done means the command completes without the JSON parser crash and produces documentation for the affected module.