npm.bbclass: Add npm class to match fetcher

npm class supports the npm fetcher, helping doing the basic compile/install
stages of an npm package

(From OE-Core rev: 4d2ad3e39242c947612023f4429bc8fb430551b5)

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/npm.bbclass

@@ -0,0 +1,25 @@
+DEPENDS_prepend = "nodejs-native "
+S = "${WORKDIR}/npmpkg"
+
+npm_do_compile() {
+	# changing the home directory to the working directory, the .npmrc will
+	# be created in this directory
+	export HOME=${WORKDIR}
+	npm config set dev false
+	npm set cache ${WORKDIR}/npm_cache
+	# clear cache before every build
+	npm cache clear
+	# Install pkg into ${S} without going to the registry
+	npm --arch=${TARGET_ARCH} --production --no-registry install
+}
+
+npm_do_install() {
+	mkdir -p ${D}${libdir}/node_modules/${PN}/
+	cp -a ${S}/* ${D}${libdir}/node_modules/${PN}/ --no-preserve=ownership
+}
+
+FILES_${PN} += " \
+    ${libdir}/node_modules/${PN} \
+"
+
+EXPORT_FUNCTIONS do_compile do_install