ci: Move Kernel build tasks into its own file

Allows to reuse the Kernel build tasks everywhere it is needed.

The x86_test-gl container now need a kernel image to use for the crosvm environment,
Reuse this task there.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10862>

.gitlab-ci/container/lava_build.sh

@@ -144,54 +144,8 @@ mv /piglit /lava-files/rootfs-${DEBIAN_ARCH}/.
 EXTRA_MESON_ARGS+=" -D prefix=/libdrm"
 . .gitlab-ci/container/build-libdrm.sh
 
-
-############### Cross-build kernel
-mkdir -p kernel
-wget -qO- ${KERNEL_URL} | tar -xj --strip-components=1 -C kernel
-pushd kernel
-
-# The kernel doesn't like the gold linker (or the old lld in our debians).
-# Sneak in some override symlinks during kernel build until we can update
-# debian (they'll get blown away by the rm of the kernel dir at the end).
-mkdir -p ld-links
-for i in /usr/bin/*-ld /usr/bin/ld; do
-    i=`basename $i`
-    ln -sf /usr/bin/$i.bfd ld-links/$i
-done
-export PATH=`pwd`/ld-links:$PATH
-
-export LOCALVERSION="`basename $KERNEL_URL`"
-./scripts/kconfig/merge_config.sh ${DEFCONFIG} ../.gitlab-ci/container/${KERNEL_ARCH}.config
-make ${KERNEL_IMAGE_NAME}
-for image in ${KERNEL_IMAGE_NAME}; do
-    cp arch/${KERNEL_ARCH}/boot/${image} /lava-files/.
-done
-
-if [[ -n ${DEVICE_TREES} ]]; then
-    make dtbs
-    cp ${DEVICE_TREES} /lava-files/.
-fi
-
-if [[ ${DEBIAN_ARCH} = "amd64" ]]; then
-    make modules
-    INSTALL_MOD_PATH=/lava-files/rootfs-${DEBIAN_ARCH}/ make modules_install
-fi
-
-if [[ ${DEBIAN_ARCH} = "arm64" ]]; then
-    make Image.lzma
-    mkimage \
-        -f auto \
-        -A arm \
-        -O linux \
-        -d arch/arm64/boot/Image.lzma \
-        -C lzma\
-        -b arch/arm64/boot/dts/qcom/sdm845-cheza-r3.dtb \
-        /lava-files/cheza-kernel
-    KERNEL_IMAGE_NAME+=" cheza-kernel"
-fi
-
-popd
-rm -rf kernel
+############### Build kernel
+. .gitlab-ci/container/build-kernel.sh
 
 ############### Delete rust, since the tests won't be compiling anything.
 rm -rf /root/.cargo