Migrate dockerfiles to use multi-stage builds.

Summary:
We previously emulated multi-staged builds using two dockerfiles,
native support from Docker allows us to merge them into one,
simplifying our scripts.

For more details about multi-stage builds, see:
https://docs.docker.com/develop/develop-images/multistage-build/

Reviewers: mehdi_amini, klimek, sammccall

Reviewed By: sammccall

Subscribers: llvm-commits, ioeric, cfe-commits

Differential Revision: https://reviews.llvm.org/D44787

llvm-svn: 328503

2 files changed, 14 insertions, 32 deletions

diff --git a/llvm/utils/docker/debian8/build/Dockerfile b/llvm/utils/docker/debian8/Dockerfile
index 3f42f2ad591..fd3bf9f49f0 100644
--- a/llvm/utils/docker/debian8/build/Dockerfile
+++ b/llvm/utils/docker/debian8/Dockerfile
@@ -6,22 +6,18 @@
 # License. See LICENSE.TXT for details.
 #
 #===----------------------------------------------------------------------===//
-# Produces an image that compiles and archives clang, based on debian8.
-FROM launcher.gcr.io/google/debian8:latest
-
+# Stage 1. Check out LLVM source code and run the build.
+FROM launcher.gcr.io/google/debian8:latest as builder
 LABEL maintainer "LLVM Developers"
-
 # Install build dependencies of llvm.
 # First, Update the apt's source list and include the sources of the packages.
 RUN grep deb /etc/apt/sources.list | \
     sed 's/^deb/deb-src /g' >> /etc/apt/sources.list
-
 # Install compiler, python and subversion.
 RUN apt-get update && \
     apt-get install -y --no-install-recommends ca-certificates gnupg \
            build-essential python wget subversion unzip && \
     rm -rf /var/lib/apt/lists/*
-
 # Install a newer ninja release. It seems the older version in the debian repos
 # randomly crashes when compiling llvm.
 RUN wget "https://github.com/ninja-build/ninja/releases/download/v1.8.2/ninja-linux.zip" && \
@@ -29,10 +25,8 @@ RUN wget "https://github.com/ninja-build/ninja/releases/download/v1.8.2/ninja-li
         | sha256sum -c  && \
     unzip ninja-linux.zip -d /usr/local/bin && \
     rm ninja-linux.zip
-
 # Import public key required for verifying signature of cmake download.
 RUN gpg --keyserver hkp://pgp.mit.edu --recv 0x2D2CEF1034921684
-
 # Download, verify and install cmake version that can compile clang into /usr/local.
 # (Version in debian8 repos is is too old)
 RUN mkdir /tmp/cmake-install && cd /tmp/cmake-install && \
@@ -47,9 +41,18 @@ RUN mkdir /tmp/cmake-install && cd /tmp/cmake-install && \
 
 ADD checksums /tmp/checksums
 ADD scripts /tmp/scripts
-
 # Arguments passed to build_install_clang.sh.
 ARG buildscript_args
-
-# Run the build. Results of the build will be available as /tmp/clang.tar.gz.
+# Run the build. Results of the build will be available at /tmp/clang-install/.
 RUN /tmp/scripts/build_install_llvm.sh ${buildscript_args}
+
+
+# Stage 2. Produce a minimal release image with build results.
+FROM launcher.gcr.io/google/debian8:latest
+LABEL maintainer "LLVM Developers"
+# Install packages for minimal useful image.
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends libstdc++-4.9-dev binutils && \
+    rm -rf /var/lib/apt/lists/*
+# Copy build results of stage 1 to /usr/local.
+COPY --from=builder /tmp/clang-install/ /usr/local/
diff --git a/llvm/utils/docker/debian8/release/Dockerfile b/llvm/utils/docker/debian8/release/Dockerfile
deleted file mode 100644
index 3a44a7d4116..00000000000
--- a/llvm/utils/docker/debian8/release/Dockerfile
+++ /dev/null
@@ -1,21 +0,0 @@
-#===- llvm/utils/docker/debian8/release/Dockerfile -----------------------===//
-#
-#                     The LLVM Compiler Infrastructure
-#
-# This file is distributed under the University of Illinois Open Source
-# License. See LICENSE.TXT for details.
-#
-#===----------------------------------------------------------------------===//
-# A release image, containing clang installation, produced by the 'build/' image
-# and adding libstdc++ and binutils.
-FROM launcher.gcr.io/google/debian8:latest
-
-LABEL maintainer "LLVM Developers"
-
-# Install packages for minimal useful image.
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends libstdc++-4.9-dev binutils && \
-    rm -rf /var/lib/apt/lists/*
-
-# Unpack clang installation into this image.
-ADD clang.tar.gz /usr/local/