fix whonix_shared/usr/share/whonix/chroot-scripts-pre.d/15_locale
build script: improved error handling, when error is detected, wait until builder presses enter before cleanup and exit to make it simpler to read error messages when building in cli
build script: error handler output
deprecated whonix_shared/usr/share/whonix/chroot-scripts-pre.d/15_locale script:
for VM builds, grml-debootstrap sets en_US.UTF-8;
for physical isolation builds, users are instructed to use United States in the installer