Add x86 Linux platform for GitHub Actions workflow

Author: jeantessier

rails_mysql/Gemfile.lock

@@ -168,6 +168,8 @@ GEM
     nio4r (2.7.3)
     nokogiri (1.16.7-arm64-darwin)
       racc (~> 1.4)
+    nokogiri (1.16.7-x86_64-linux)
+      racc (~> 1.4)
     orm_adapter (0.5.0)
     packwerk (3.2.1)
       activesupport (>= 6.0)
@@ -316,6 +318,7 @@ GEM
 
 PLATFORMS
   arm64-darwin-23
+  x86_64-linux
 
 DEPENDENCIES
   bootsnap