Support in the Dockerfile for Etheno's new support of Node 12

Dockerfile

@@ -2,6 +2,9 @@ FROM trailofbits/etheno:latest
 MAINTAINER Evan Sultanik
 
 USER root
+ENV HOME="/root"
+ENV PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+WORKDIR /root
 
 # Remove the version of solc installed by Etheno
 RUN apt-get -y remove solc
@@ -11,6 +14,15 @@ RUN bash /install_solc.sh && rm /install_solc.sh
 # Install the solc-selection script:
 COPY solc-select /usr/bin/
 
+# Slither now requires npx
+# Also install Embark while we are at it
+
+RUN npm install --force -g \
+    embark \
+    @trailofbits/embark-contract-info \
+    n && \
+    n stable && n prune && npm --force cache clean
+
 WORKDIR /home
 
 RUN usermod -l ethsec etheno
@@ -29,18 +41,6 @@ RUN solc-select --list | tail -n1 | xargs solc-select
 RUN mv examples etheno-examples
 
 RUN pip3 --no-cache-dir install slither-analyzer pyevmasm
-# Slither now requires npx
-# Also install Embark while we are at it
-USER root
-RUN apt-get update && apt-get -y install npm && rm -rf /var/lib/apt/lists/*
-
-RUN npm -g install npx \
-    embark \
-    @trailofbits/embark-contract-info \
-    n && \
-    n stable && n prune && npm cache clean
-
-USER ethsec
 
 RUN git clone --depth 1 https://github.com/trailofbits/not-so-smart-contracts.git && \
     git clone --depth 1 https://github.com/trailofbits/rattle.git && \