Merge pull request #147 from kilpatty/dockerfile-fix-gmp

docker: add gmp-dev to fix compilation issues on Alpine

Author: chjj

Dockerfile

@@ -12,7 +12,7 @@ COPY package.json \
 
 # Install build dependencies and compile
 FROM base AS build
-RUN apk add --no-cache g++ gcc make python2
+RUN apk add --no-cache g++ gcc make python2 gmp-dev
 RUN npm install --production
 
 FROM base