Fix ISO build failure by updating bootmodes

The ISO build was failing with the error `_make_bootmode_: command not found`. This was caused by an outdated `bootmodes` configuration in `profiledef.sh` that is no longer compatible with recent versions of `archiso`.

This commit updates the `bootmodes` array to use the new, simplified format (`'bios.syslinux'` and `'uefi.systemd-boot'`) as specified in the latest `archiso` documentation. This resolves the build failure.

Author: google-labs-jules[bot]

profiledef.sh

@@ -8,7 +8,7 @@ iso_application="Arch Linux No Beep Live/Rescue DVD"
 iso_version="$(date --date="@${SOURCE_DATE_EPOCH:-$(date +%s)}" +%Y.%m.%d)"
 install_dir="arch"
 buildmodes=('iso')
-bootmodes=('bios.syslinux.mbr,bios.syslinux.eltorito,uefi-ia32.systemd-boot.esp,uefi-x64.systemd-boot.esp,uefi-ia32.systemd-boot.eltorito,uefi-x64.systemd-boot.eltorito')
+bootmodes=('bios.syslinux' 'uefi.systemd-boot')
 arch="x86_64"
 pacman_conf="pacman.conf"
 airootfs_image_type="squashfs"