Install ccache symlinks

The ccache formula now installs ccache symlinks for a number of
compilers into the #{libexec} directory.  By adding this
directory to your PATH, ccache will automatically be used for most
compilations.  The list of compilers matches that in the current
MacPorts ccache portfile.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

* Added caveats
* libexec isn't linked in to HOMEBREW_PREFIX, so it is private enough
  without a subfolder

Formula/ccache.rb

@@ -9,5 +9,32 @@ class Ccache <Formula
     system "./configure", "--prefix=#{prefix}", "--mandir=#{man}"
     system "make"
     system "make install"
+
+    # Install symlinks for a variety of compilers into
+    # #{libexec}/ccache.  Prepending this directory to your
+    # PATH should automatically activate ccache for most compiles.
+
+    ohai "Creating symbolic links"
+
+    libexec.mkpath
+
+    %w[
+      cc
+      gcc gcc2 gcc3 gcc-3.3 gcc-4.0
+      c++ c++3 c++-3.3 c++-4.0
+      g++ g++2 g++3 g++-3.3 g++-4.0
+    ].each do |prog|
+      ln_s bin+"ccache", libexec + prog
+    end
+  end
+
+  def caveats
+    <<-EOS
+      To install symlinks for compilers that will automatically use
+      ccache, add this folder to the front of your PATH:
+        #{libexec}
+
+      NOTE: ccache can prevent some software from compiling.
+    EOS
   end
 end