garbage appended to sourcelink.json

[ctaggart]

Not sure why, but locally, I'm getting a d4/*}} added to the end of the sourcelink.json for fsautocomplete when using SourceLink.Create.CommandLine 2.6.0. The other two work just fine. We'll see if if is just my system or if it happens on AppVeyor too.

ionide/FsAutoComplete#266

C:\Users\camer\cs\SourceLink\build [master ≡]> dotnet sourcelink test "C:\Users\camer\fs\FsAutoComplete\bin\release_netcore\fsautocomplete.pdb"
Additional text encountered after finished reading JSON content: d. Path '', line 1, position 158.
C:\Users\camer\cs\SourceLink\build [master ≡]> dotnet sourcelink print-json "C:\Users\camer\fs\FsAutoComplete\bin\release_netcore\fsautocomplete.pdb"
{"documents":{"C:\\Users\\camer\\fs\\FsAutoComplete\\*":"https://raw.githubusercontent.com/fsharp/FsAutoComplete/e712ddb03b3df46138223124f141b28c76804556/*"}}d4/*"}}