Add missing log_error function for DEB packaging

- log_error() function was used in DEB packaging block but not defined
- Added function definition after log_info() at script top
- Fixes 'log_error: command not found' error in DEB packaging stage

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/new_docker_build_release2.sh

@@ -88,6 +88,10 @@ log_info() {
   echo "[INFO] $*"
 }
 
+log_error() {
+  printf 'ERROR: %s\n' "$*" >&2
+}
+
 die() {
   echo "[ERROR] $*" >&2
   exit 1