Do not delete dist folder before build or .tsbuildinfo files afterwards

Typescript supports incremental compilation, we even have it [enabled by default](https://github.com/ipfs/aegir/blob/master/src/config/tsconfig.aegir.json#L15), but it works by looking up a `.tsbuildinfo` from the [configured outDir](https://github.com/ipfs/aegir/blob/master/src/config/tsconfig.aegir.json#L5).

Aegir [deletes](https://github.com/ipfs/aegir/blob/master/src/build/index.js#L56-L59) the `dist` folder before every build and the [.tsbuildinfo](https://github.com/ipfs/aegir/blob/master/src/ts/index.js#L163) file after the build so incremental compilation is not possible.

Disabling these deletions locally made the first build time for the full js-IPFS monorepo of about 10 minutes drop to 2 minutes on subsequent builds.

`.tsbuildinfo` files should be omitted from publishing by adding an exclude to the `files` array in a project's `package.json`:

```
"files": [
"src",
"dist",
"!dist/*.tsbuildinfo"
],