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>

diff -durN strace-4.5.19.orig/syscall.c strace-4.5.19/syscall.c

--- strace-4.5.19.orig/syscall.c	2009-10-28 18:47:18.000000000 +0100

+++ strace-4.5.19/syscall.c	2009-10-28 18:47:18.000000000 +0100

@@ -110,6 +110,18 @@

 #define TP TRACE_PROCESS

 #define TS TRACE_SIGNAL

+#ifndef HAVE_STATFS64

+/*

+ * Ugly hacks for systems that do not have LFS

+ */

+

+#define sys_truncate64  sys_truncate

+#define sys_ftruncate64 sys_ftruncate

+#define sys_getdents64  sys_getdents

+#define sys_statfs64    sys_statfs

+#define sys_fstatfs64   sys_fstatfs

+#endif

+

 static const struct sysent sysent0[] = {

 #include "syscallent.h"

 };