build_kernel_deb: Really fail on unknown board types

build/build_kernel_deb.sh

@@ -90,7 +90,7 @@ case "${pureos_board}" in
     DOT_CONFIG=librem5-evk_defconfig
     GIT_OPTS=(--depth 1)
     ;;
-  \?)
+  *)
     echo "unrecognized board type ${pureos_board}"
     exit 1
     ;;