Don't know how this escaped from mkmf.rb but it misses several DESTDIR
prefixes in exec_prefix and libdir which particulary insuitable for
packaging (rpm, deb, ...) of Ruby extensions.

diff -urNk.orig ruby-1.6.5/lib/mkmf.rb.orig ruby-1.6.5/lib/mkmf.rb
--- ruby-1.6.5/lib/mkmf.rb.orig	Fri Aug 17 08:04:33 2001
+++ ruby-1.6.5/lib/mkmf.rb	Fri Nov 30 15:33:24 2001
@@ -449,8 +449,8 @@
 end
 }
 prefix = $(DESTDIR)#{CONFIG["prefix"].sub(drive, '')}
-exec_prefix = #{CONFIG["exec_prefix"].sub(drive, '')}
-libdir = #{$libdir.sub(drive, '')}
+exec_prefix = $(DESTDIR)#{CONFIG["exec_prefix"].sub(drive, '')}
+libdir = $(DESTDIR)#{$libdir.sub(drive, '')}
 rubylibdir = #{$rubylibdir.sub(drive, '')}
 archdir = #{$archdir.sub(drive, '')}
 sitedir = #{$sitedir.sub(drive, '')}

-- 
/ Alexander Bokovoy
$ cat /proc/identity >~/.signature
  `Senior software developer and analyst for SaM-Solutions Ltd.`
---
Nov 21 20:58:58 alconost kernel: VFS: Busy inodes after unmount. 
		    Self-destruct in 5 seconds.  Have a nice day...