Add option that allows to clear build log panel automatically with rebuild

I use the bottom panel build log a lot, since it contains important information about build issues. Rust is a bit verbose here.

My workflow kinda looks like this

• Click "clear" button to get rid of old build log
• Rebuild project
• scroll to the beginning of the log, since the first compiler/log entry is often the most relevant one

It would be neat to have something, which clears the build log automatically, when the project gets rebuilt. At the moment I'm clearing the build everytime by hand. Without clearing it, it's a bit cumbersome to find the beginning of the new build log (since the old log still exists).