package/luarocks: fix copying our custom command if dest dir exists

Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>
[yann.morin.1998@free.fr:
  - use $(INSTALL), not "mkdir -p + cp"
  - split to its own patch
  - rewrite commit title
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/luarocks/luarocks.mk

@@ -17,8 +17,7 @@ LUAROCKS_CONFIG_FILE = $(LUAROCKS_CONFIG_DIR)/luarocks/config.lua
 HOST_LUAROCKS_CONFIG_FILE = $(LUAROCKS_CONFIG_DIR)/luarocks/host-config.lua
 
 define LUAROCKS_ADDON_EXTRACT
-	mkdir $(@D)/src/luarocks/cmd/external
-	cp package/luarocks/buildroot.lua $(@D)/src/luarocks/cmd/external/buildroot.lua
+	$(INSTALL) -D -m 0644 package/luarocks/buildroot.lua $(@D)/src/luarocks/cmd/external/buildroot.lua
 endef
 HOST_LUAROCKS_POST_EXTRACT_HOOKS += LUAROCKS_ADDON_EXTRACT