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
diff --git a/llvm/utils/docker/scripts/build_install_llvm.sh b/llvm/utils/docker/scripts/build_install_llvm.sh
index 67e537fa..7e5ac1e 100755
--- a/llvm/utils/docker/scripts/build_install_llvm.sh
+++ b/llvm/utils/docker/scripts/build_install_llvm.sh
@@ -16,8 +16,8 @@
 
 Checkout svn sources and run cmake with the specified arguments. Used
 inside docker container.
-Passes additional -DCMAKE_INSTALL_PREFIX and archives the contents of
-the directory to /tmp/clang.tar.gz.
+Passes additional -DCMAKE_INSTALL_PREFIX and puts the build results into
+/tmp/clang-install/ directory.
 
 Available options:
   -h|--help           show this help message
@@ -244,12 +244,7 @@
 
 popd
 
-# Pack the installed clang into an archive.
-echo "Archiving clang installation to /tmp/clang.tar.gz"
-cd "$CLANG_INSTALL_DIR"
-tar -czf /tmp/clang.tar.gz *
-
 # Cleanup.
-rm -rf "$CLANG_BUILD_DIR" "$CLANG_INSTALL_DIR"
+rm -rf "$CLANG_BUILD_DIR"
 
 echo "Done"