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>

# This file declares functions to install the kernel headers for mingw

# Copyright 2009 Bart vdr. Meulen

# Licensed under the GPL v2. See COPYING in the root of this package

CT_DoKernelTupleValues() {

    CT_TARGET_KERNEL="mingw32"

    CT_TARGET_SYS=

}

do_kernel_get() {

    CT_GetFile "w32api-${CT_W32API_VERSION}-mingw32-src" \

        http://downloads.sourceforge.net/sourceforge/mingw

}

do_kernel_extract() {

    CT_Extract "w32api-${CT_W32API_VERSION}-mingw32-src"

}

do_kernel_headers() {

    CT_DoStep INFO "Installing kernel headers"

    mkdir -p "${CT_HEADERS_DIR}"

    cp -r ${CT_SRC_DIR}/w32api-${CT_W32API_VERSION}-mingw32-src/include/*   \

          ${CT_HEADERS_DIR}

    CT_EndStep

}