Introduce ENV.O2 and use that for the postgresql build

Also only set ARCHFLAGS on non-Core Duo machines... though it seemed to build
fine even with it, it doenst make much sense to me... these changes are kind
of up for debate but it "works for me" this way...

Closes Homebrew/homebrew#75

Formula/postgresql.rb

@@ -20,15 +20,19 @@ class Postgresql <Formula
         "--disable-debug"
     ]
 
-    if MACOS_VERSION >= 10.6
-      configure_args << "ARCHFLAGS='-arch x86_64'"
+    if MACOS_VERSION >= 10.6 && Hardware.is_64_bit?
+        configure_args << "ARCHFLAGS='-arch x86_64'"
+    end
+
+    # Fails on Core Duo with O4 and O3
+    if Hardware.intel_family == :core
+      ENV.O2
     end
 
     system "./configure", *configure_args
     system "make install"
 
     (prefix+'org.postgresql.postgres.plist').write startup_plist
-
   end
 
   def skip_clean? path