extension: kernel-version-toolchain for compiler in artifact version

Add opt-in extension that includes gcc/clang major.minor version in the
kernel artifact version string for cache invalidation when the toolchain
changes. Enable with ENABLE_EXTENSIONS="kernel-version-toolchain".

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: 2 people

extensions/kernel-version-toolchain.sh

@@ -0,0 +1,35 @@
+# Add compiler (gcc/clang) identifier to kernel artifact version string.
+# This ensures cache invalidation when the toolchain changes.
+# Enable with: ENABLE_EXTENSIONS="kernel-version-toolchain"
+
+function artifact_kernel_version_parts__add_toolchain() {
+	# Determine compiler binary
+	declare kernel_compiler_bin="${KERNEL_COMPILER}gcc"
+	if [[ "${KERNEL_COMPILER}" == "clang" ]]; then
+		kernel_compiler_bin="clang"
+	fi
+
+	# Get compiler version (major.minor only)
+	declare toolchain_id="unknown"
+	if command -v "${kernel_compiler_bin}" &> /dev/null; then
+		declare full_version
+		full_version="$(${kernel_compiler_bin} -dumpfullversion -dumpversion 2>/dev/null || echo "")"
+		if [[ -n "${full_version}" ]]; then
+			# Extract major.minor, drop patch version
+			declare short_version
+			short_version="$(echo "${full_version}" | cut -d'.' -f1-2)"
+			# Build identifier: gcc13.3 or clang18.1
+			if [[ "${KERNEL_COMPILER}" == "clang" ]]; then
+				toolchain_id="clang${short_version}"
+			else
+				toolchain_id="gcc${short_version}"
+			fi
+		fi
+	fi
+
+	display_alert "Extension: ${EXTENSION}: Adding toolchain to kernel version" "${toolchain_id}" "debug"
+
+	# Add to version parts
+	artifact_version_parts["_T"]="${toolchain_id}"
+	artifact_version_part_order+=("0085-_T")
+}

lib/functions/artifacts/artifact-kernel.sh

@@ -131,7 +131,7 @@ function artifact_kernel_prepare_version() {
 	# tac reverses order so last becomes first, then sort -uk keeps first occurrence of each key.
 	declare -a kernel_config_modifying_hashes_reduced=()
 	mapfile -t kernel_config_modifying_hashes_reduced < <(
-		printf '%s\n' "${kernel_config_modifying_hashes[@]}" | tac | LC_ALL=C sort -t '=' -uk 1,1
+		printf '%s\n' "${kernel_config_modifying_hashes[@]}" | tac | LC_ALL=C sort -s -t '=' -uk 1,1
 	)
 	kernel_config_modification_hash="$(printf '%s\n' "${kernel_config_modifying_hashes_reduced[@]}" | sha256sum | cut -d' ' -f1)"
 	kernel_config_modification_hash="${kernel_config_modification_hash:0:16}" # "long hash"