el directorio base es el sitio mismo

app/models/deploy.rb

@@ -35,6 +35,14 @@ class Deploy < ApplicationRecord
     (@stop - @start).round(3)
   end
 
+  def home_dir
+    site.path
+  end
+
+  def gems_dir
+    Pathname.new(File.join(home_dir, '..', 'gems')).realpath.to_s
+  end
+
   # Corre un comando y devuelve true si terminó correctamente
   # rubocop:disable Metrics/MethodLength
   # rubocop:disable Metrics/AbcSize

app/models/deploy_local.rb

@@ -43,7 +43,11 @@ class DeployLocal < Deploy
     # XXX: This doesn't support Windows paths :B
     paths = [File.dirname(`which bundle`), '/usr/bin']
 
-    { 'PATH' => paths.join(':'), 'JEKYLL_ENV' => 'production' }
+    {
+      'HOME' => home_dir,
+      'PATH' => paths.join(':'),
+      'JEKYLL_ENV' => 'production'
+    }
   end
 
   def yarn_lock
@@ -62,7 +66,7 @@ class DeployLocal < Deploy
   end
 
   def bundle
-    run 'bundle install --path=../gems'
+    run %(bundle install --path="#{gems_dir}")
   end
 
   def jekyll_build