spidermonkey: remove use of autoconf

Closes Homebrew/legacy-homebrew#20296.

Formula/spidermonkey.rb

@@ -1,13 +1,5 @@
 require 'formula'
 
-# Private older version of autoconf required to compile Spidermonkey
-class Autoconf213 < Formula
-  homepage 'http://www.gnu.org/software/autoconf/'
-  url 'http://ftpmirror.gnu.org/autoconf/autoconf-2.13.tar.gz'
-  mirror 'http://ftp.gnu.org/gnu/autoconf/autoconf-2.13.tar.gz'
-  sha1 'e4826c8bd85325067818f19b2b2ad2b625da66fc'
-end
-
 class Spidermonkey < Formula
   homepage 'https://developer.mozilla.org/en/SpiderMonkey'
   url 'http://ftp.mozilla.org/pub/mozilla.org/js/js185-1.0.0.tar.gz'
@@ -24,21 +16,7 @@ def install
     # penryn (core 2 duo) CPU. So lets be cautious here and remove it.
     ENV['CFLAGS'] = ENV['CFLAGS'].gsub(/-msse[^\s]+/, '') if MacOS.version == :leopard
 
-    # For some reason SpiderMonkey requires Autoconf-2.13
-    ac213_prefix = buildpath/'ac213'
-    Autoconf213.new.brew do |f|
-      # Force use of plain "awk"
-      inreplace 'configure', 'for ac_prog in mawk gawk nawk awk', 'for ac_prog in awk'
-
-      system "./configure", "--disable-debug",
-                            "--program-suffix=213",
-                            "--prefix=#{ac213_prefix}"
-      system "make install"
-    end
-
     cd "js/src" do
-      system "#{ac213_prefix}/bin/autoconf213"
-
       # Remove the broken *(for anyone but FF) install_name
       inreplace "config/rules.mk",
         "-install_name @executable_path/$(SHARED_LIBRARY) ",