Add support for building on crossroads.

[brugger1]

Description

Resolves #19337

I added more support for building on crossroads. Specific items include:

1. Modifying build_visit to build on crossroads.
2. Adding a config-site file for crossroads.
3. Removing support for building on trinity and adding support for building on crossroads to run-build-visit.

Type of change

• New feature~~

How Has This Been Tested?

1. I used run-build-visit to build the third party libraries on crossroads in public.
2. I untarred the visit3.4.2.tar.gz generated from this branch.
3. I made some changes to winutil/WindowMetrics.C so that it would compile since the Qt6 built on crossroads didn't have xcb support.
4. I commented out the packaging of libQt6XcbQpa.so and the xcbglintegrations so that make package worked.
5. I ran make package to build a distribution.
6. I installed the distribution.
7. I tested VisIt in serial to create an image with -cli -nowin because VisIt couldn't be run with the GUI because of the Qt6 issue. It created the image visit0000.png, which I successfully viewed.
8. I tested VisIt in parallel to create an image with -cli -nowin. It created the image visit0001.png, which I successfully viewed. I ran this test totally in a parallel batch allocation since there is no network path between a compute node and a login node (to my knowledge at least).

Even though not everything in VisIt currently works, it tests the changes made.

Reminders:

• Please follow the style guidelines of this project.
• Please perform a self-review of your code before submitting a PR and asking others to review it.
• Please assign reviewers (see VisIt's PR procedures for more information).

Checklist:

• I have commented my code where applicable.~~
• [ ] I have updated the release notes.
• [ ] I have made corresponding changes to the documentation.
• [ ] I have added debugging support to my changes.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have confirmed new and existing unit tests pass locally with my changes.
• [ ] I have added new baselines for any new tests to the repo.
• I have NOT made any changes to protocol or public interfaces in an RC branch.~~

[markcmiller86]

Thanks for doing all this, @brugger1 ❤️