brew-config: show realpath for pyenv and rbenv

Closes Homebrew/homebrew#35819.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/cmd/config.rb

@@ -74,11 +74,21 @@ module Homebrew
   end
 
   def describe_python
-    describe_path(which 'python')
+    python = which 'python'
+    if %r{/shims/python$} =~ python && which('pyenv')
+      "#{python} => #{Pathname.new(`pyenv which python`.strip).realpath}" rescue describe_path(python)
+    else
+      describe_path(python)
+    end
   end
 
   def describe_ruby
-    describe_path(which 'ruby')
+    ruby = which 'ruby'
+    if %r{/shims/ruby$} =~ ruby && which('rbenv')
+      "#{ruby} => #{Pathname.new(`rbenv which ruby`.strip).realpath}" rescue describe_path(ruby)
+    else
+      describe_path(ruby)
+    end
   end
 
   def hardware