Text on Buttons and Labels is Invisible for Linux Installer

Problem

After starting the Linux installer, the text on buttons and labels is invisible.

This seems to be a font issue between Oracle Java SE 8 (bundled with the installer) and Fedora/Gnome.

There are two possible workarounds:

Run the installer with the default (non-native) Java L&F by using the -Dinstall4j.nolaf=true argument. For example:
```
oxygen-64bit-openjdk.sh -Dinstall4j.nolaf=true
```
Run the installer in console mode using the -c argument. For example:
```
oxygen-64bit-openjdk.sh -c
```