Vcsbase: Commit and Diff buttons have elided text (Windows style, Qt 5.12)

The buttons in the Commit/Amend editor have elided text, for no reason. This happens only in the Qt 5.12-based Qt Creator builds and apparently only with the Windows style, without dpi scaling.

I believe this is a Qt 5.12 specific issue, but was not able to quickly create a mini example to reproduce this. Therefore, It is for now a Qt Creator issue.