Add CentOS 7 + Devtoolset 7 image

Ref: Level/leveldown#672

Author: rvagg

README.md

@@ -9,6 +9,7 @@
 ### [`prebuild/linux-arm64`](https://hub.docker.com/r/prebuild/linux-arm64)
 ### [`prebuild/linux-armv7`](https://hub.docker.com/r/prebuild/linux-armv7)
 ### [`prebuild/alpine`](https://hub.docker.com/r/prebuild/alpine)
+### [`prebuild/centos7-devtoolset7`](https://hub.docker.com/r/prebuild/centos7-devtoolset7)
 
 ## License
 

centos7-devtoolset7/Dockerfile

@@ -0,0 +1,13 @@
+FROM centos/devtoolset-7-toolchain-centos7
+
+USER 0
+
+RUN groupadd -g 1000 node && useradd -g 1000 -u 1000 -m node && \
+  groupadd -g 2000 travis && useradd -g 2000 -u 2000 -m travis
+
+RUN curl -sL https://rpm.nodesource.com/setup_12.x | bash - && \
+  yum install -y nodejs
+
+USER node
+
+WORKDIR /opt/app-root

centos7-devtoolset7/Makefile

@@ -0,0 +1,5 @@
+build:
+	docker build -t prebuild/centos7-devtoolset7 .
+
+push:
+	docker push prebuild/centos7-devtoolset7