Add command-check to get-bdf2u8g.sh

buildroot/share/fonts/get-bdf2u8g.sh

 
 HERE=$(pwd)
 
+for CMD in curl unzip patch make; do
+  which $CMD >/dev/null || { echo "'$CMD' is required for this script." ; exit 1 ; }
+done
+
 [[ $HERE =~ 'buildroot/share/fonts'$ ]] || { echo "Change to buildroot/share/fonts to run $(basename $0)" ; exit 1; }
 
 # Download u8glib