kernel/linux: fix using custom location

Currently, extract and patch are skipped as thus:
- using a custom directory of pre-installed headers
- a correctly named directory already exists

Otherwise, extract and patch are done.

The current second condition is wrong, because it allows the following
sequence to happen:
- a non-custom kernel is used
- a previous build only partially extracted the non-custom sources
- that p[revious build broke during extraction (eg. incomplete tarball...)
- a subsequent build will find a properly named directory, and will
thus skip extract and patch, which is wrong

Fix that by following the conditions in this table:

Type | Extract | Patch
----------------------+---------+-------
Pre-installed headers | N | N
custom directory | N | N
custom tarball | Y | N
mainstream tarball | Y | Y

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: David Holsgrove <david.holsgrove@xilinx.com>

 2011-02-28  Aurelien Jarno  <aurelien@aurel32.net>

 	* sysdeps/alpha/stackinfo.h: Define DEFAULT_STACK_PERMS with PF_X.

 diff --git glibc-2.13/glibc-ports-2.13/sysdeps/alpha/stackinfo.h glibc-2.13/glibc-ports-2.13/sysdeps/alpha/stackinfo.h

 index 0a281bd..d9dbc35 100644

 --- glibc-2.13/glibc-ports-2.13/sysdeps/alpha/stackinfo.h

 +++ glibc-2.13/glibc-ports-2.13/sysdeps/alpha/stackinfo.h

 @@ -22,7 +22,13 @@

  #ifndef _STACKINFO_H

  #define _STACKINFO_H	1

 +#include <elf.h>

 +

  /* On Alpha the stack grows down.  */

  #define _STACK_GROWS_DOWN	1

 +/* Default to an executable stack.  PF_X can be overridden if PT_GNU_STACK is

 + * present, but it is presumed absent.  */

 +#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)

 +

  #endif	/* stackinfo.h */