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/glibc-ports-2.7.orig/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h	2007-06-06 19:27:04.000000000 +0200

+++ glibc-2.7/glibc-ports-2.7/sysdeps/unix/sysv/linux/arm/nptl/sysdep-cancel.h	2008-05-18 16:57:21.000000000 +0200

@@ -73,6 +73,9 @@

 # define DOCARGS_5	DOCARGS_4

 # define UNDOCARGS_5	UNDOCARGS_4

+# define DOCARGS_6    DOCARGS_5

+# define UNDOCARGS_6  UNDOCARGS_5

+

 # ifdef IS_IN_libpthread

 #  define CENABLE	bl PLTJMP(__pthread_enable_asynccancel)

 #  define CDISABLE	bl PLTJMP(__pthread_disable_asynccancel)