scons: revert to standalone install

Closes Homebrew/homebrew#23807.

Formula/scons.rb

@@ -5,18 +5,23 @@ class Scons < Formula
   url 'http://downloads.sourceforge.net/scons/scons-2.3.0.tar.gz'
   sha1 '728edf20047a9f8a537107dbff8d8f803fd2d5e3'
 
-  depends_on :python
-
   def install
     man1.install gzip('scons-time.1', 'scons.1', 'sconsign.1')
-    python do
+    system "/usr/bin/python", "setup.py", "install",
-      system python, "setup.py", "install",
              "--prefix=#{prefix}",
              "--standalone-lib",
              # SCons gets handsy with sys.path---`scons-local` is one place it
              # will look when all is said and done.
+             "--install-lib=#{libexec}/scons-local",
+             "--install-scripts=#{bin}",
              "--install-data=#{libexec}",
              "--no-version-script", "--no-install-man"
+
+    # Re-root scripts to libexec so they can import SCons and symlink back into
+    # bin. Similar tactics are used in the duplicity formula.
+    bin.children.each do |p|
+      mv p, "#{libexec}/#{p.basename}.py"
+      bin.install_symlink "#{libexec}/#{p.basename}.py" => p.basename
     end
   end
 end