Remove dependency on curl

This is part of the transition towards providing cross platform support for caching and build artifacts (see #298 (closed)). This MR adds the ability to upload build artifacts using the build runner itself, thus removing the dependency on curl (which is not reliably available across all platforms).


  • Add implementation for uploading multipart form encoded file to build artifact API
  • Explicitly set the Content-Length header
  • Set request mime type correctly
  • Add a command which triggers the uploading of a provided file
  • Switch Bash to use the built in uploader
  • TEST!