R: Add option for Valgrind-enabled debug build

Useful for developing packages that interact with R at the C level.

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

Formula/r.rb

@@ -1,20 +1,42 @@
 require 'formula'
 
+def valgrind?
+  ARGV.include? '--with-valgrind'
+end
+
 class R < Formula
   url 'http://cran.r-project.org/src/base/R-2/R-2.13.0.tar.gz'
   homepage 'http://www.R-project.org/'
   md5 'ecfb928067cfd932e75135f8b8bba3e7'
 
+  depends_on 'valgrind' if valgrind?
+
+  def options
+    [
+      ['--with-valgrind', 'Compile an unoptimized build with support for the Valgrind debugger.']
+    ]
+  end
+
   def install
+    if valgrind?
+      ENV.remove_from_cflags /-O./
+      ENV.append_to_cflags '-O0'
+    end
+
     ENV.fortran
     ENV.x11 # So PNG gets added to the x11 and cairo plotting devices
     ENV['OBJC'] = ENV['CC']
     ENV['OBJCFLAGS'] = ENV['CFLAGS']
 
-    system "./configure", "--prefix=#{prefix}",
-                          "--with-aqua",
-                          "--enable-R-framework",
-                          "--with-lapack"
+    args = [
+      "--prefix=#{prefix}",
+      "--with-aqua",
+      "--enable-R-framework",
+      "--with-lapack"
+    ]
+    args << '--with-valgrind-instrumentation=2' if valgrind?
+
+    system "./configure", *args
     system "make"
     ENV.j1 # Serialized installs, please
     system "make install"