Update kernel builder to work with kernels 6.6 and later. Add 6.8.x to kernel build list (#1992)

Summary: Update kernel builder to work with kernels 6.6 and later. Add
6.8.x to kernel build list

Sicne Ubuntu's current LTS release runs on a 6.8.x kernel, I wanted to
keep our newest kernel version in line with that. If/when this is
approved, I'll proceed with running the
[upload](https://github.com/pixie-io/pixie/blob/33244cd28d79058792a6cc06fe2637f491cd51a7/tools/docker/Makefile#L288)
(side stepping the GCS part) and then add this to the
[all_kernel_versions](https://github.com/pixie-io/pixie/blob/33244cd28d79058792a6cc06fe2637f491cd51a7/ci/github/matrix.sh#L31)
ci matrix.

Relevant Issues: N/A

Type of change: /kind feature

Test Plan: Ran the makefile target for an older and newer kernel to
verify it works now

---------

Signed-off-by: Dom Del Nano <ddelnano@gmail.com>

Author: ddelnano

tools/docker/Makefile

@@ -128,10 +128,11 @@ KERNEL_BUILD_DIR := $(BUILD_DIR)/kernel_build
 # 4.19.276, 4.14.304 are the correct versions here, but there is a bug with patch > 255.
 KERNEL_BUILD_VERSIONS := 4.14.254 \
 	4.19.254 \
-	5.4.235 \
-	5.10.173 \
-	5.15.101 \
-	6.1.18
+	5.4.254 \
+	5.10.224 \
+	5.15.165 \
+	6.1.106 \
+	6.8.12
 
 KERNEL_BUILD_TEMPLATE := linux-build-%.tar.gz
 KERNEL_BUILD_TARGETS = $(addprefix $(KERNEL_BUILD_DIR)/, $(patsubst %,$(KERNEL_BUILD_TEMPLATE), $(KERNEL_BUILD_VERSIONS)))

tools/docker/kernel_builder/build_kernel.sh

@@ -119,6 +119,12 @@ module_path="${pkg_dir}/root/lib/modules/${KERNEL_VERSION}"
 module_build_path="${module_path}/build"
 module_source_path="${module_path}/source"
 
+# linux 6.6 removed the source symlink from the modules_install target.
+# Add in to keep compatibility with older kernels and our build process.
+# https://github.com/torvalds/linux/commit/d8131c2965d5ee59bfa4d548641e52a13cbe17c9
+if [[ ! -L "${module_source_path}" ]]; then
+    ln -s "${kernel_source_dir}" "${module_source_path}"
+fi
 create_unlinked_dir "${module_build_path}"
 create_unlinked_dir "${module_source_path}"