Update build time estimate.

doc/src/sgml/installation.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.272 2007/01/18 14:07:31 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/installation.sgml,v 1.273 2007/01/20 17:21:29 petere Exp $ -->
 
 <chapter id="installation">
  <title><![%standalone-include[<productname>PostgreSQL</>]]>
@@ -1245,7 +1245,7 @@ su - postgres
 <userinput>gmake</userinput>
 </screen>
     (Remember to use <acronym>GNU</> <application>make</>.) The build
-    may take anywhere from 5 minutes to half an hour depending on your
+    will take a few minutes depending on your
     hardware. The last line displayed should be
 <screen>
 All of PostgreSQL is successfully made. Ready to install.