Update development steps (#1623)

Ensure the development steps can be successfully executed with system
ruby on Fedora 36 to try and help new contributors have an easier
on-ramp.

Support running acceptance tests locally, though note that it may
require rvm if vagrant doesn't support the ruby version used by the
distro.

spec/spec_helper.rb

@@ -41,10 +41,18 @@ end
 RSpec.configure do |config|
   require 'tmpdir'
 
-  # set VAGRANT_HOME before any thing that requires vagrant is loaded to prevent
-  # the global plugin manager from trying to use the default VAGRANT_HOME.
-  temp_dir = Dir.mktmpdir("rspec-")
-  ENV['VAGRANT_HOME'] = temp_dir
+  if ENV['VAGRANT_LIBVIRT_VAGRANT_HOME'].nil?
+    # set VAGRANT_HOME before any thing that requires vagrant is loaded to prevent
+    # the global plugin manager from trying to use the default VAGRANT_HOME.
+    temp_dir = Dir.mktmpdir("rspec-")
+    ENV['VAGRANT_HOME'] = temp_dir
+  else
+    ENV['VAGRANT_HOME'] = ENV['VAGRANT_LIBVIRT_VAGRANT_HOME']
+  end
+
+  # acceptance tests need the boxes dir to exist to allow symlinking of isolated
+  # environments while allowing the boxes to be cached.
+  FileUtils.mkdir_p(File.join(ENV['VAGRANT_HOME'], 'boxes'))
 
   # ensure that setting of LIBVIRT_DEFAULT_URI in the environment is not picked
   # up directly by tests, instead they must set as needed. Some build envs will

spec/support/acceptance/isolated_environment.rb

@@ -30,7 +30,7 @@ module VagrantPlugins
 
           # Execute, logging out the stdout/stderr as we get it
           @logger.info("Executing: #{[command].concat(args).inspect}")
-          Vagrant::Spec::Subprocess.execute(command, *args, **options) do |type, data|
+          Vagrant::Spec::Subprocess.new(command, *args, **options).execute do |type, data|
             @logger.debug("#{type}: #{data}") if type == :stdout || type == :stderr
             yield type, data if block_given?
           end

spec/support/libvirt_acceptance_context.rb

@@ -22,7 +22,7 @@ shared_context 'libvirt_acceptance' do
 
   before(:each) do
     # allow execution environment to cache boxes used
-    symlink_boxes(ENV.fetch('VAGRANT_HOME', nil), environment)
+    symlink_boxes(ENV.fetch('VAGRANT_HOME', File.expand_path('~/.vagrant.d')), environment)
   end
 
   after(:each) do