setup/hg: handle hg being a symlink when appending relative libdir to sys.path

Resolve symbolic links in the path to hg so that an hg that works when
invoked directly will also work when invoked via a symlink to it.

hg

@@ -1,37 +1,38 b''
 #!/usr/bin/env python
 #
 # mercurial - scalable distributed SCM
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import os
 import sys
 
 libdir = '@LIBDIR@'
 
 if libdir != '@' 'LIBDIR' '@':
     if not os.path.isabs(libdir):
-        libdir = os.path.join(os.path.dirname(__file__), libdir)
+        libdir = os.path.join(os.path.dirname(os.path.realpath(__file__)),
+                              libdir)
         libdir = os.path.abspath(libdir)
     sys.path.insert(0, libdir)
 
 # enable importing on demand to reduce startup time
 try:
     from mercurial import demandimport; demandimport.enable()
 except ImportError:
     import sys
     sys.stderr.write("abort: couldn't find mercurial libraries in [%s]\n" %
                      ' '.join(sys.path))
     sys.stderr.write("(check your install and PYTHONPATH)\n")
     sys.exit(-1)
 
 import mercurial.util
 import mercurial.dispatch
 
 for fp in (sys.stdin, sys.stdout, sys.stderr):
     mercurial.util.set_binary(fp)
 
 mercurial.dispatch.run()