Fix extension installer for out-of-place build

hsbt · k0kubun · commit 8dda932bcded · 2024-05-28T13:30:26.000-07:00
#9673 (comment)
diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
@@ -784,7 +784,12 @@ def ext_features
         end
 
         def makefile_path
-          "#{makefile_dir}/Makefile"
+          if File.exist?("#{makefile_dir}/Makefile")
+            "#{makefile_dir}/Makefile"
+          else
+            # for out-of-place build
+            "#{$ext_build_dir}/#{relative_base}/Makefile"
+          end
         end
 
         def makefile_dir
