add -nographic flag for x86_64 arch

[thebigbone]

Add -nographic in build_library/qemu_template.sh

Refer flatcar/Flatcar#1687

Testing done

• Use the flag to boot up flatcar linux image on a headless x86_64 system and it works fine.

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)

• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

[chewi]

I was actually looking to go the other way and remove -nographic from all cases, as having the display can help diagnose some early boot issues. There were some driver-related issues with arm64 though, so I didn't push it yet. You can always add -- -nographic yourself if that's what you want.

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/13947661546

[chewi]

Maybe we could make this automatic by checking the DISPLAY and WAYLAND_DISPLAY variables.

[jepio]

I manually provide either -nographic or -display curses on the flatcar_production_qemu.sh command line. One reason for the arm64/amd64 difference in -nographic: on arm64 the default console is the serial console, and on amd64 the default is tty0/tty1. So to get early kernel/initrd console output in -nographic mode on amd64 requires breaking in grub and appending console=ttyS0 to the kernel command line.