message: Do less unnecessary work on CI
  We were checking out & installing the develop js-sdk explicitly
  in cases where we didn't need it at all. We were babeling the src
  folder many, many times over (in some cases twice in the same job)
  and never using the output at all.
diff: @@ -6,9 +6,9 @@ scripts/fetchdep.sh matrix-org matrix-js-sdk
  pushd matrix-js-sdk
  yarn link
  -yarn install
  +yarn install $@
  yarn build
  popd
  yarn link matrix-js-sdk
  -yarn install
  +yarn install $@
  