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>

--- strace-orig/file.c	2008/05/20 04:56:18	1.92

+++ strace/file.c	2008/08/01 01:13:10	1.93

@@ -28,21 +28,22 @@

  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  *

- *	$Id: file.c,v 1.92 2008/05/20 04:56:18 roland Exp $

+ *	$Id: file.c,v 1.93 2008/08/01 01:13:10 roland Exp $

  */

 #include "defs.h"

 #include <dirent.h>

+

 #ifdef LINUX

-#define dirent kernel_dirent

-#define dirent64 kernel_dirent64

-#include <linux/types.h>

-#include <linux/dirent.h>

-#undef dirent

-#undef dirent64

+struct kernel_dirent {

+	unsigned long   d_ino;

+	unsigned long   d_off;

+	unsigned short  d_reclen;

+	char            d_name[1];

+};

 #else

-#define kernel_dirent dirent

+# define kernel_dirent dirent

 #endif

 #ifdef LINUX