globally change build directory on linux?

[falams]

Currently I'm changing it per project with Projects -> Properties menu, but globally anywhere in $HOME would be nice.

While not related, I've been using KDE with KDE's "Breeze Dark" theme and while it changes the background of the editor to black, certain syntax highlighting options won't work. In particular, the line highlighting doesn't work so finding which column the cursor is at is just a guess. So, is there any plans to change syntax highlighting for dark themes?