fix: removed empty lines from the build stdout

[tabarra]

Since #195 yarn stdout is printing one empty line for every stdout event, causing blank lines like shown below.
Before: https://i.imgur.com/0rbnKXv.png
After: https://i.imgur.com/0baqrX2.png

I'm doing regex replace instead of .trim() to preserve any multiline output with indentation or something like that.
Note that the code assumes every event will be a new line, and only a single line. If one event has multiple lines then the [yarn] tag will be broken.
On second thought, probably better to even remove it since now all resource outputs are already tagged?! Let me know and can push a new commit removing it.