Support execution of npm prepare scripts in Docker container

Workaround suggested in npm/npm#18163.

Author: erikap

Dockerfile

@@ -12,7 +12,7 @@ WORKDIR /usr/src/app
 COPY . /usr/src/app
 
 RUN ln -s /app/app.js /usr/src/app/
-RUN npm install
+RUN npm config set unsafe-perm true && npm install
 
 CMD sh boot.sh
 
@@ -23,4 +23,4 @@ ONBUILD RUN if [ -f /app/on-build.sh ]; \
         && chmod +x /app/on-build.sh \
         && /bin/bash /app/on-build.sh ;\
      fi
-ONBUILD RUN if [ -f "/app/package.json" ]; then npm install /app; fi
+ONBUILD RUN if [ -f "/app/package.json" ]; then npm config set unsafe-perm true && npm install /app; fi

boot.sh

@@ -7,7 +7,7 @@ then
         -x sh start.sh
 else
     ## Install new dependencies
-    if [ -f "/app/package.json" ]; then npm install /app; fi
+    if [ -f "/app/package.json" ]; then npm config set unsafe-perm true && npm install /app; fi
     ## Boot the app in development mode
     ./node_modules/supervisor/lib/cli-wrapper.js \
         -w /usr/src/app,/app \