Initial commit. Unusable Marlin 2.0.5.3 core without any custimization.

buildroot/bin/opt_enable

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+# exit on first failure
+set -e
+
+SED=$(which gsed || which sed)
+
+for opt in "$@" ; do
+  # Logic for returning nonzero based on answer here: https://stackoverflow.com/a/15966279/104648
+  eval "${SED} -i '/\(\/\/\)*[[:blank:]]*\(#define \b${opt}\b\)/{s//\2/;h};\${x;/./{x;q0};x;q9}' Marlin/Configuration.h" ||
+  eval "${SED} -i '/\(\/\/\)*[[:blank:]]*\(#define \b${opt}\b\)/{s//\2/;h};\${x;/./{x;q0};x;q9}' Marlin/Configuration_adv.h" ||
+  (echo "ERROR: opt_enable Can't find ${opt}" >&2 && exit 9)
+done