Add Docker image and example using docker-compose (#32)

* Create Dockerfile
  This follows all the intructions for llvm and makes it possilble to start making reproducible builds

* Create docker-compose.yml to compile and run an example project

* Simplify example so that it can be run without user input

* Copy files from repo into container
  This makes it nice for building an image based on the current repo, not the latest HEAD

* Link llvm-cbe so it's in PATH

* Improve hello_world test example

* Improve build time using Ninja and curling sources / prebuilt binaries

* Update Dockerfile to install ninja and cmake using apt

Author: dfrankland

Dockerfile

@@ -0,0 +1,26 @@
+FROM buildpack-deps:stretch
+
+RUN \
+  set -e; \
+  apt update && apt install -y \
+    clang \
+    ninja-build \
+    cmake; \
+  cd /root; \
+  curl -fL http://releases.llvm.org/7.0.1/llvm-7.0.1.src.tar.xz \
+    | tar xJf -; \
+  mv /root/llvm-7.0.1.src /root/llvm; \
+  mkdir -p /root/llvm/build;
+
+COPY . /root/llvm/projects/llvm-cbe/
+
+RUN \
+  set -e; \
+  mkdir -p /root/llvm/build; \
+  cd /root/llvm/build; \
+  cmake -G Ninja -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ..; \
+  ninja llvm-cbe; \
+  ninja lli; \
+  ninja CBEUnitTests; \
+  /root/llvm/build/projects/llvm-cbe/unittests/CWriterTest; \
+  ln -s /root/llvm/build/bin/llvm-cbe /bin/llvm-cbe;

docker-compose.yml

@@ -0,0 +1,27 @@
+version: "3"
+
+services:
+  llvm-cbe:
+    build: .
+    working_dir: /root
+    volumes:
+      - ./test:/test
+    command: |
+      bash -c "
+        set -e;
+
+        # Navigate to test folder
+        cd /test/hello_world;
+
+        # Compile main.c to llvm IR
+        clang -S -emit-llvm main.c;
+
+        # Compile llvm IR back to C
+        llvm-cbe main.ll;
+
+        # Compile llvm-cbe generated C code
+        gcc -g -o main.cbe main.cbe.c;
+
+        # Run it
+        ./main.cbe;
+      "

test/hello_world/.gitignore

@@ -0,0 +1,3 @@
+*
+!.gitignore
+!main.c

test/hello_world/main.c

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+#include <stdio.h>
+
+int main() {
+   printf("Hello, World!\n");
+   return 0;
+}