Makefile: delete debug libs when debug is not enabled

Some toolchains, like the Linaro gcc7 toolchains, now install libstdc++ debug
library symbols to /lib/debug, which can be as large as the library itself.
This commit removes the extra debug content if debugging is not enabled.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 04e9a1ec8c0dee17728f7a213855bef2f8300b64)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Makefile

@@ -766,6 +766,9 @@ endif
 	rm -rf $(TARGET_DIR)/usr/doc $(TARGET_DIR)/usr/share/doc
 	rm -rf $(TARGET_DIR)/usr/share/gtk-doc
 	rmdir $(TARGET_DIR)/usr/share 2>/dev/null || true
+ifneq ($(BR2_ENABLE_DEBUG):$(BR2_STRIP_strip),y:)
+	rm -rf $(TARGET_DIR)/lib/debug $(TARGET_DIR)/usr/lib/debug
+endif
 	$(STRIP_FIND_CMD) | xargs -0 $(STRIPCMD) 2>/dev/null || true
 	$(STRIP_FIND_SPECIAL_LIBS_CMD) | xargs -0 -r $(STRIPCMD) $(STRIP_STRIP_DEBUG) 2>/dev/null || true