scripts: Fix flash linux when OUT argument provided (#6133)

Signed-off-by: Ilya Vislotsky <write2ilya@gmail.com>

scripts/flash-linux.sh

@@ -7,10 +7,17 @@ if [ "$EUID" -ne 0 ]; then
 fi
 set -e
 
+# Setting build output directory
+if [ -z "${1}" ]; then
+    out='out'
+else
+    out=${1}
+fi
+
 # Install new micro-controller code
 echo "Installing micro-controller code to /usr/local/bin/"
 rm -f /usr/local/bin/klipper_mcu
-cp out/klipper.elf /usr/local/bin/klipper_mcu
+cp ${out}/klipper.elf /usr/local/bin/klipper_mcu
 sync
 
 # Restart (if system install script present)