Add script to fall back to source build

package.json

@@ -19,7 +19,7 @@
     "test": "npm run lint && node ./node_modules/cucumber/bin/cucumber.js features/ -p verify && node ./node_modules/cucumber/bin/cucumber.js features/ -p mld",
     "clean": "rm -rf test/cache",
     "docs": "./scripts/build_api_docs.sh",
-    "install": "node-pre-gyp install --fallback-to-build=false",
+    "install": "node-pre-gyp install --fallback-to-build=false || ./scripts/node_install.sh",
     "nodejs-tests": "make -C test/data && ./lib/binding/osrm-datastore test/data/ch/monaco.osrm && node test/nodejs/index.js | faucet"
   },
   "repository": {

scripts/node_install.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+set -e
+
+CMAKE_OPTIONS=${CMAKE_OPTIONS:-"-DCMAKE_BUILD_TYPE=Release -DENABLE_NODE_BINDINGS=On -DENABLE_MASON=On"}
+
+if [[ ! -f $(which cmake) ]]; then
+    echo "Needs cmake to build from source"
+    exit 1
+fi
+if [[ ! -f $(which clang) ]]; then
+    echo "Needs clang to build from source"
+    exit 1
+fi
+if [[ ! -f $(which clang++) ]]; then
+    echo "Needs clang++ to build from source"
+    exit 1
+fi
+
+if [[ -d build ]]; then
+    echo "Detected existing build directory, skipping compiling."
+    exit 0
+else
+    mkdir -p build
+    pushd build
+    CXX=clang++ CC=clang cmake .. $CMAKE_OPTIONS
+    popd
+fi