doctor: remove autotools check

Library/Homebrew/diagnostic.rb

@@ -1100,22 +1100,6 @@ module Homebrew
         end
       end
 
-      def check_for_autoconf
-        return unless MacOS::Xcode.installed?
-        return unless MacOS::Xcode.provides_autotools?
-
-        autoconf = which("autoconf")
-        safe_autoconfs = %w[/usr/bin/autoconf /Developer/usr/bin/autoconf]
-        return if autoconf.nil? || safe_autoconfs.include?(autoconf.to_s)
-
-        <<-EOS.undent
-          An "autoconf" in your path blocks the Xcode-provided version at:
-            #{autoconf}
-
-          This custom autoconf may cause some Homebrew formulae to fail to compile.
-        EOS
-      end
-
       def __check_linked_brew(f)
         f.installed_prefixes.each do |prefix|
           prefix.find do |src|

Library/Homebrew/test/test_diagnostic.rb

@@ -204,20 +204,6 @@ class DiagnosticChecksTest < Homebrew::TestCase
     HOMEBREW_CELLAR.mkpath
   end
 
-  def test_check_for_autoconf
-    MacOS::Xcode.stubs(:installed?).returns true
-    MacOS::Xcode.stubs(:provides_autotools?).returns true
-    mktmpdir do |path|
-      file = "#{path}/autoconf"
-      FileUtils.touch file
-      FileUtils.chmod 0755, file
-      ENV["PATH"] = [path, ENV["PATH"]].join File::PATH_SEPARATOR
-
-      assert_match "This custom autoconf",
-        @checks.check_for_autoconf
-    end
-  end
-
   def test_check_tmpdir
     ENV["TMPDIR"] = "/i/don/t/exis/t"
     assert_match "doesn't exist",