Change output path to be picked up by artifact upload

Because Gitlab CI can't upload artifacts from outside the build dir, and Go by default builds outside of that, we need to output to the build dir for artifact upload.

Thanks! Makes sense!

merged

This should be in quotes: "$CI_PROJECT_DIR/mybinary", also: since cwd is $CI_PROJECT_DIR why this is needed?

cc @dvdmuckle @zj

In tests, my Go binary was not picked up when built with arguments similar to the previous template. Outputting to $CI_PROJECT_DIR/mybinary and picking up the artifact mybinary worked. As for the use of quotes, I defer that choice to you and @zj.