Makefile: Run npm install when necessary

Also mark phony targets as such.

Makefile

@@ -1,6 +1,6 @@
 PACKAGE_NAME := $(shell python3 -c "import json; print(json.load(open('package.json'))['name'])")
 
-all:
+all: node_modules/react-lite
 	NODE_ENV=$(NODE_ENV) npm run build
 
 clean:
@@ -40,3 +40,8 @@ rpm: dist-gzip
 	find `pwd`/output -name '*.rpm' -printf '%f\n' -exec mv {} . \;
 	rm -r "`pwd`/rpmbuild"
 	rm -r "`pwd`/output" "`pwd`/build"
+
+node_modules/react-lite:
+	npm install
+
+.PHONY: all clean install install-only dist-gzip srpm rpm

README.md

@@ -4,9 +4,8 @@ Scaffolding for a [Cockpit](http://www.cockpit-project.org) module.
 
 # Building
 
-Run `npm install` to install dependencies and `make` to build the package. It
-builds into the `dist` directory. Link or copy that to a location were
-`cockpit-bridge` looks for packages.
+Run `make` to build the package. It builds into the `dist` directory. Link or
+copy that to a location were `cockpit-bridge` looks for packages.
 
 `make install` compiles and installs the package in `/usr/share/cockpit/`. The
 convenience targets `srpm` and `rpm` build the source and binary rpms,