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>

--- glibc-2.7/sysdeps/unix/sysv/linux/sh/sysdep.S.orig	2005-12-30 22:16:43.000000000 +0000

+++ glibc-2.7/sysdeps/unix/sysv/linux/sh/sysdep.S	2008-08-19 22:33:14.000000000 +0100

@@ -32,3 +32,13 @@

 #define __syscall_error __syscall_error_1

 #include <sysdeps/unix/sh/sysdep.S>

+

+	.data

+	.align 3

+	.globl ___fpscr_values

+	.type ___fpscr_values, @object

+	.size ___fpscr_values, 8

+___fpscr_values:

+	.long	0

+	.long	0x80000

+weak_alias (___fpscr_values, __fpscr_values)

--- glibc-2.7/sysdeps/unix/sysv/linux/sh/Versions.orig	2003-09-01 05:05:09.000000000 +0100

+++ glibc-2.7/sysdeps/unix/sysv/linux/sh/Versions	2008-08-19 22:33:14.000000000 +0100

@@ -2,6 +2,7 @@

   GLIBC_2.2 {

     # functions used in other libraries

     __xstat64; __fxstat64; __lxstat64;

+    __fpscr_values;

     # a*

     alphasort64;