kbuild: Hack for depmod not handling X.Y versions

depmod from module-init-tools < 3.13 and the busybox depmod check if the
kernel release starts with <num>.<num>.<num>. To support these versions,
we create a symlink with two numbers prepended.
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/depmod.sh

@@ -18,8 +18,31 @@ fi
 if ! test -r System.map -a -x "$DEPMOD"; then
 	exit 0
 fi
+# older versions of depmod require the version string to start with three
+# numbers, so we cheat with a symlink here
+depmod_hack_needed=true
+mkdir -p .tmp_depmod/lib/modules/$KERNELRELEASE
+if "$DEPMOD" -b .tmp_depmod $KERNELRELEASE 2>/dev/null; then
+	if test -e .tmp_depmod/lib/modules/$KERNELRELEASE/modules.dep -o \
+		-e .tmp_depmod/lib/modules/$KERNELRELEASE/modules.dep.bin; then
+		depmod_hack_needed=false
+	fi
+fi
+if $depmod_hack_needed; then
+	symlink="$INSTALL_MOD_PATH/lib/modules/99.98.$KERNELRELEASE"
+	ln -s "$KERNELRELEASE" "$symlink"
+	KERNELRELEASE=99.98.$KERNELRELEASE
+fi
+
 set -- -ae -F System.map
 if test -n "$INSTALL_MOD_PATH"; then
 	set -- "$@" -b "$INSTALL_MOD_PATH"
 fi
-exec "$DEPMOD" "$@" "$KERNELRELEASE"
+"$DEPMOD" "$@" "$KERNELRELEASE"
+ret=$?
+
+if $depmod_hack_needed; then
+	rm -f "$symlink"
+fi
+
+exit $ret