build: always add extra entry for newLinesIndices

[keegancsmith]

This was a regression in the recent change. If the file ended in a newline we didn't add an extra index entry, which lead to us returning the "linenum for entry out of range" error.

Test Plan: caught this on my ranking integration tests branch

[keegancsmith]

@jtibshirani I know you have been deploying new versions of zoekt and monitoring indexing. You may have come across this accidental regression by me. Here is the fix :)

[jtibshirani]

Oops! Would it be easy to add a regression test for this, for example just index a file with an extra newline?

[keegancsmith]

hmm, so the behaviour is different from before but this is an example of universal-ctags just outputing incorrect data. I am closing this PR and have an alternative fix here #694

Check universal-ctags says this symbol is on line 22 but line 22 doesn't exist:

$ universal-ctags '--fields=*' --output-format=json main.ts | grep 22
{"_type": "tag", "name": "config", "path": "main.ts", "pattern": "/^export default config$/", "language": "TypeScript", "line": 22, "kind": "constant", "roles": "def"}

$ wc -l main.ts 
21 main.ts

$ tail -n1 main.ts 
export default config