Changed Dockerfiles to install LLVM into /usr/local

Summary:
Previously, the installation path was simply '/'.
Using '/usr/local' would ensure that LLVM installation does not
conflict with software installed via package managers.

Reviewers: mehdi_amini, klimek

Reviewed By: klimek

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37213

llvm-svn: 311890

llvm/utils/docker/debian8/release/Dockerfile

@@ -18,4 +18,4 @@ RUN apt-get update && \
     rm -rf /var/lib/apt/lists/*
 
 # Unpack clang installation into this image.
-ADD clang.tar.gz /
+ADD clang.tar.gz /usr/local/

llvm/utils/docker/example/release/Dockerfile

@@ -21,4 +21,4 @@ LABEL maintainer "Maintainer <maintainer@email>"
 
 # Unpack clang installation into this container.
 # It is copied to this directory by build_docker_image.sh script.
-ADD clang.tar.gz /
+ADD clang.tar.gz /usr/local/

llvm/utils/docker/nvidia-cuda/release/Dockerfile

@@ -18,6 +18,6 @@ FROM nvidia/cuda:8.0-devel
 LABEL maintainer "LLVM Developers"
 
 # Unpack clang installation into this container.
-ADD clang.tar.gz /
+ADD clang.tar.gz /usr/local/
 
 # C++ standard library and binutils are already included in the base package.