Exclude system_tests group when running release prep in GH

GitHub runners don't have libcurl headers installed, which is needed by faraday
1.x -> patron. Omit the system_tests group when running release prep in GH (both
GITHUB_ACTIONS will be set and GITHUB_WORKFLOW_REF will contain the absolute
path to the workflow file).

Author: joshcooper

Gemfile

@@ -76,13 +76,18 @@ group :development, :release_prep do
   gem "puppetlabs_spec_helper", '~> 8.0', require: false
   gem "puppet-blacksmith", '~> 7.0',      require: false
 end
-# We are overriding the default PDK template's Litmus logic in order to use the
-# latest Bolt in tests. See PA-7824.
-group :system_tests do
-  gem "puppet_litmus", '~> 2.0',      require: false, platforms: [:ruby, :x64_mingw]
-  gem "CFPropertyList", '< 3.0.7',    require: false, platforms: [:mswin, :mingw, :x64_mingw]
-  gem "serverspec", '~> 2.41',        require: false
-  gem "voxpupuli-acceptance", '~> 3', require: false
+# On GitHub Actions, only resolve system_tests gems for the task_acceptance_tests
+# workflow to avoid native-extension (faraday-patron/libcurl4) failures in
+# workflows that don't need them (release_prep, unit_tests, static_code_analysis).
+unless ENV['GITHUB_ACTIONS'] && !ENV.fetch('GITHUB_WORKFLOW_REF', '').include?('task_acceptance_tests.yaml')
+  # We are overriding the default PDK template's Litmus logic in order to use the
+  # latest Bolt in tests. See PA-7824.
+  group :system_tests do
+    gem "puppet_litmus", '~> 2.0',      require: false, platforms: [:ruby, :x64_mingw]
+    gem "CFPropertyList", '< 3.0.7',    require: false, platforms: [:mswin, :mingw, :x64_mingw]
+    gem "serverspec", '~> 2.41',        require: false
+    gem "voxpupuli-acceptance", '~> 3', require: false
+  end
 end
 
 gems = {}