--watch is broken in release-2.0.5

[vladima]

1. create file app.ts
2. start compiler in watch mode, i.e. node built/local/tsc.js --watch app.ts
3. save the file

Expected: no errors, output file is written
Actual: error error TS5033: Could not write file 'app.js': ENOENT: no such file or directory, mkdir '' occured
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