target-finalize: avoid stripping kernel modules with incorrect permissions

If a kernel module is installed with incorrect permissions (0755 iso 0644),
it would get stripped in a way that would render the kernel module broken.
While the incorrect permissions are a developer error, it is a minor change
to prevent this mistake from causing incorrectly stripped modules.

This was reported with bug #6992:
https://bugs.busybox.net/show_bug.cgi?id=6992

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Makefile

@@ -507,7 +507,14 @@ ifneq (,$(call qstrip,$(BR2_STRIP_EXCLUDE_DIRS)))
 STRIP_FIND_CMD += \( $(call finddirclauses,$(TARGET_DIR),$(call qstrip,$(BR2_STRIP_EXCLUDE_DIRS))) \) -prune -o
 endif
 STRIP_FIND_CMD += -type f \( -perm /111 -o -name '*.so*' \)
-STRIP_FIND_CMD += -not \( $(call findfileclauses,libpthread*.so* $(call qstrip,$(BR2_STRIP_EXCLUDE_FILES))) \) -print
+# file exclusions:
+# - libpthread.so: a non-stripped libpthread shared library is needed for
+#   proper debugging of pthread programs using gdb.
+# - kernel modules (*.ko): do not function properly when stripped like normal
+#   applications and libraries. Normally kernel modules are already excluded
+#   by the executable permission check above, so the explicit exclusion is only
+#   done for kernel modules with incorrect permissions.
+STRIP_FIND_CMD += -not \( $(call findfileclauses,libpthread*.so* *.ko $(call qstrip,$(BR2_STRIP_EXCLUDE_FILES))) \) -print
 
 $(TARGETS_ROOTFS): target-finalize