fix make clean for windows

diff --git a/build/common.mk b/build/common.mk
index 01f152d..6599646 100755 (executable)
--- a/build/common.mk
+++ b/build/common.mk
@@ -283,7 +283,7 @@ size: $(OUTDIR)/$(PROJECT).elf
 
 clean:
        @echo Cleaning up all build generated files
-       $(Q) $(REMOVE_DIR) $(OUTDIR) $(QUIET)
+       $(Q) $(REMOVE_DIR) $(call convert-slash,$(OUTDIR)) $(QUIET)
 
 -include $(DEPFILES)