Revert "RbConfig: fix broken MacOS SDK paths"

This reverts commit 11445e0f.

Library/Homebrew/extend/rbconfig_extension.rb

-# typed: false
-# frozen_string_literal: true
-
-macos_version = ENV["HOMEBREW_MACOS_VERSION"][0..4]
-macos_sdk = "MacOSX#{macos_version}.sdk"
-
-# Ruby hardcodes what might end up being an incorrect SDK path in some of the
-# variables that get used in mkmf.rb.
-# This patches them up to use the correct SDK.
-RbConfig::CONFIG.each do |k, v|
-  next unless v.include?("MacOSX.sdk")
-
-  new_value = v.gsub("MacOSX.sdk", macos_sdk)
-  next unless File.exist?(new_value)
-
-  RbConfig::CONFIG[k] = new_value
-end

Library/Homebrew/utils/gems.rb

@@ -109,15 +109,6 @@ module Homebrew
     install_bundler!
 
     ENV["BUNDLE_GEMFILE"] = File.join(ENV.fetch("HOMEBREW_LIBRARY"), "Homebrew", "Gemfile")
-
-    # We can't use OS.mac? because not enough has
-    # been required yet this early in the boot process
-    if ENV["HOMEBREW_SYSTEM"] == "Macintosh"
-      # This patches up some paths used by mkmf.rb
-      extend_path = File.join(ENV.fetch("HOMEBREW_LIBRARY"), "Homebrew", "extend")
-      ENV["RUBYOPT"] = "-r#{extend_path}/rbconfig_extension"
-    end
-
     @bundle_installed ||= begin
       bundle = File.join(find_in_path("bundle"), "bundle")
       bundle_check_output = `#{bundle} check 2>&1`
@@ -135,8 +126,6 @@ module Homebrew
       end
     end
 
-    ENV["RUBYOPT"] = ""
-
     setup_gem_environment!
   end
 end