node-arduino-firmata: copy files, not symlinks

This was meant to be included in 6ed62c6, but wasn't.
Current version of npm install installs a link to the build directory.
The workaround is to use npm pack to make a tarball and install from
that.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

lang/node-arduino-firmata/Makefile

@@ -49,12 +49,13 @@ endef
 EXTRA_LDFLAGS="-L$(TOOLCHAIN_DIR)/lib/ -Wl,-rpath-link $(TOOLCHAIN_DIR)/lib/" \
 
 define Build/Compile
+	cd $(PKG_BUILD_DIR) ; \
 	$(MAKE_FLAGS) \
 	npm_config_arch=$(CONFIG_ARCH) \
 	npm_config_nodedir=$(BUILD_DIR)/node-$(PKG_NODE_VERSION)/ \
 	npm_config_cache=$(BUILD_DIR)/node-$(PKG_NODE_VERSION)/npm-cache \
 	PREFIX="$(PKG_INSTALL_DIR)/usr/" \
-	npm install -g $(PKG_BUILD_DIR)
+	npm install -g `npm pack $(PKG_BUILD_DIR) | tail -n 1`
 endef
 
 define Package/node-arduino-firmata/install