Headless Tests in CI try to load shared libraries

[Marius Hanl]

Hi,

I recently tried to write headless tests by utilizing the new headless platform.
First of all, works great!

I noticed that the CI still tries to load shared libraries. This will fail in 
the CI with the following message:

Loading library prism_es2 from resource failed: 
java.lang.UnsatisfiedLinkError: 
/root/.openjfx/cache/26-ea+7/amd64/libprism_es2.so: Error loading shared 
library libX11.so.6: No such file or directory (needed by 
/root/.openjfx/cache/26-ea+7/amd64/libprism_es2.so)
java.lang.UnsatisfiedLinkError: 
/root/.openjfx/cache/26-ea+7/amd64/libprism_es2.so: Error loading shared 
library libX11.so.6: No such file or directory (needed by 
/root/.openjfx/cache/26-ea+7/amd64/libprism_es2.so)
    at java.base/jdk.internal.loader.NativeLibraries.load(Native Method)
    at 
java.base/jdk.internal.loader.NativeLibraries$NativeLibraryImpl.open(NativeLibraries.java:321)
...


The tests still run and work regardless, but I wonder if this can be disabled. 
If not, if that's a feasible enhancement for headless tests?
Thoughts?

-- Marius