Pass skipLibCheck to tsc in ts_web_library (#407)
Pass skipLibCheck to tsc in ts_web_library (#407)

skipLibCheck means that the TypeScript compiler will not check `.d.ts` files for
internal correctness. It will only check their use in `.ts` files.

This works around two issues:
- With certain inputs, Clutz will produce inconsistent `.d.ts` files. The
  problems are cosmetic insofar as using the APIs generated works and checks
  correctly, just the `.d.ts` doesn't check out internally. As no user wrote
  that code, it doesn't make sense to check it.
- TypeScript initially reads large declaration files such as `lib.d.ts`. That
  takes a lot of time, so this change will speed up compilation.

This change unblocks an upgrade of Clutz in google3.
agrubb/tensorboard,tensorflow/tensorboard,agrubb/tensorboard,ioeric/tensorboard,qiuminxu/tensorboard,agrubb/tensorboard,francoisluus/tensorboard-supervise,agrubb/tensorboard,francoisluus/tensorboard-supervise,ioeric/tensorboard,ioeric/tensorboard,qiuminxu/tensorboard,tensorflow/tensorboard,qiuminxu/tensorboard,tensorflow/tensorboard,qiuminxu/tensorboard,tensorflow/tensorboard,ioeric/tensorboard,agrubb/tensorboard,francoisluus/tensorboard-supervise,ioeric/tensorboard,francoisluus/tensorboard-supervise,ioeric/tensorboard,francoisluus/tensorboard-supervise,qiuminxu/tensorboard,agrubb/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,francoisluus/tensorboard-supervise,qiuminxu/tensorboard