api/tsserverlibrary.d.ts generated by jake and gulp differ

[sheetalkamat]

TypeScript Version: 3.4.0-dev.201xxxxx

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when running tests for api, the baseline for api/tsserverlibrary.d.ts is different with jake and gulp.
Jake generates ExternalProject::getExcludedFiles() return type as

getExcludedFiles(): readonly NormalizedPath[];

while gulp generates it as:

getExcludedFiles(): ReadonlyArray<NormalizedPath>;

Note the return type is inferred so seems like one is using lib/tsserver.js and other is using built/local/tsserver.js
Expected behavior:

Actual behavior:

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[sheetalkamat]

@rbuckton @weswigham can you please look.

[ahejlsberg]

Wes and I were looking at this yesterday. It's because gulp uses the LKG compiler to generate the API files where jake uses the locally built compiler. I think we should just use the LKG compiler always and then make sure to update LKG before we release anything.