Auto-create libraries directory when ensuring installation of arduino backend

Author: ianfixes

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 ### Added
+- `ensure_arduino_installation.rb` now ensures the existence of the library directory as well
 
 ### Changed
 - Conserve CI testing minutes by grouping CI into fewer runs

exe/ensure_arduino_installation.rb

@@ -2,4 +2,10 @@
 require 'arduino_ci'
 
 # this will exit after Arduino is located and/or forcibly installed
-ArduinoCI::ArduinoInstallation.autolocate!
+backend = ArduinoCI::ArduinoInstallation.autolocate!
+lib_dir = backend.lib_dir
+
+unless lib_dir.exist?
+  puts "Creating libraries directory #{lib_dir}"
+  lib_dir.mkpath
+end