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>

# Build script for libtool

CT_LIBTOOL_VERSION=2.2.6b

do_companion_tools_libtool_get() {

    CT_GetFile "libtool-${CT_LIBTOOL_VERSION}" \

               {ftp,http}://ftp.gnu.org/gnu/libtool

}

do_companion_tools_libtool_extract() {

    CT_Extract "libtool-${CT_LIBTOOL_VERSION}"

    CT_DoExecLog ALL chmod -R u+w "${CT_SRC_DIR}/libtool-${CT_LIBTOOL_VERSION}"

    CT_Patch "libtool" "${CT_LIBTOOL_VERSION}"

}

do_companion_tools_libtool_build() {

    CT_DoStep EXTRA "Installing libtool"

    mkdir -p "${CT_BUILD_DIR}/build-libtool"

    CT_Pushd "${CT_BUILD_DIR}/build-libtool"

    CT_DoExecLog CFG \

    "${CT_SRC_DIR}/libtool-${CT_LIBTOOL_VERSION}/configure" \

        --prefix="${CT_BUILDTOOLS_PREFIX_DIR}"

    CT_DoExecLog ALL make

    CT_DoExecLog ALL make install

    CT_Popd

    CT_EndStep

}