kbuild: deb-pkg: Don't fail if modules.order is missing

Kernels built without CONFIG_MODULES might still want to create -dbg deb
packages but install_linux_image_dbg() assumes modules.order always
exists. This obviously isn't true if no modules were built, so we should
skip reading modules.order in that case.

Fixes: 16c36f8 ("kbuild: deb-pkg: use build ID instead of debug link for dbg package")
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Author: mfleming

scripts/package/builddeb

@@ -96,16 +96,18 @@ install_linux_image_dbg () {
 
 	# Parse modules.order directly because 'make modules_install' may sign,
 	# compress modules, and then run unneeded depmod.
-	while read -r mod; do
-		mod="${mod%.o}.ko"
-		dbg="${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/kernel/${mod}"
-		buildid=$("${READELF}" -n "${mod}" | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
-		link="${pdir}/usr/lib/debug/.build-id/${buildid}.debug"
-
-		mkdir -p "${dbg%/*}" "${link%/*}"
-		"${OBJCOPY}" --only-keep-debug "${mod}" "${dbg}"
-		ln -sf --relative "${dbg}" "${link}"
-	done < modules.order
+	if is_enabled CONFIG_MODULES; then
+		while read -r mod; do
+			mod="${mod%.o}.ko"
+			dbg="${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/kernel/${mod}"
+			buildid=$("${READELF}" -n "${mod}" | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+			link="${pdir}/usr/lib/debug/.build-id/${buildid}.debug"
+
+			mkdir -p "${dbg%/*}" "${link%/*}"
+			"${OBJCOPY}" --only-keep-debug "${mod}" "${dbg}"
+			ln -sf --relative "${dbg}" "${link}"
+		done < modules.order
+	fi
 
 	# Build debug package
 	# Different tools want the image in different locations