Robuster string parsing in bash script

In the `avrdude` call the elf-file input argument is used:
"... -Uflash:w:$1:e".
On some systems the "$1:e" is interpreted as the extension of this
argument, i.e. only producing "elf" instead of the full
"<path-to_elf.elf>"

Adding curly braces "${1]:e" ensures robust parsing.

Author: jackonelli

flash.sh

@@ -13,4 +13,4 @@ if [ "$#" -lt 1 ]; then
 fi
 
 sudo -u $USER cargo build
-avrdude -q -C/etc/avrdude.conf -patmega328p -carduino -P/dev/ttyACM0 -D "-Uflash:w:$1:e"
+avrdude -q -C/etc/avrdude.conf -patmega328p -carduino -P/dev/ttyACM0 -D "-Uflash:w:${1}:e"