Drop host composer dependency

Author: oxyc

Vagrantfile

@@ -13,7 +13,6 @@ if File.exist?("#{host_project_dir}/composer.json")
   cconfig = load_composer_config("#{host_project_dir}/composer.json")
 
   # If Drupal VM is a Composer dependency set the correct path.
-  vendor_dir = `composer config vendor-dir`.strip
   drupalvm_path = "#{vendor_dir}/geerlingguy/drupal-vm"
   if Dir.exist?("#{host_project_dir}/#{drupalvm_path}")
     host_drupalvm_dir = "#{host_project_dir}/#{drupalvm_path}"

lib/drupalvm/vagrant.rb

@@ -66,6 +66,16 @@ def ansible_version
   /^[^\s]+ (.+)$/.match(`#{ansible_bin} --version`) { |match| return match[1] }
 end
 
+# Return the path to the composer executable
+def composer_bin
+  @composer_bin ||= which('composer')
+end
+
+# Return Composer's vendor directory.
+def vendor_dir
+  @vendor_dir ||= composer_bin ? `#{composer_bin} config vendor-dir`.strip : 'vendor'
+end
+
 # Require that if installed, the ansible version meets the requirements.
 def require_ansible_version(requirement)
   return unless ansible_bin