Add Habitat plan.sh for x86_64-linux-musl

To build the package you have to have habitat install and then run:
```
$ hab pkg build . -k chef
```

You will get a `.hart` package inside `results/` that you can install on
any Linux x86_64.

Spun up a Redhat 6.5 and install it:
```
[root@localhost ~]# hab install /chef-delivery-cli-0.0.1-20170126223932-x86_64-linux.hart
✓ Installed core/cacerts/2016.09.14/20161031044952
✓ Installed core/musl/1.1.14/20161214032430
✓ Installed core/openssl-musl/1.0.2j/20161214065445
✓ Installed core/zlib-musl/1.2.8/20161214065420
✓ Installed chef/delivery-cli/0.0.1/20170126223932
★ Install of chef/delivery-cli/0.0.1/20170126223932 complete with 5 new packages installed.
[root@localhost ~]# /hab/pkgs/chef/delivery-cli/0.0.1/20170126223932/bin/delivery --version
delivery 0.0.0 (0000)
```

Next steps could be to make the installer install the package in the
right location. Maybe even make one for OSX. 😄

Signed-off-by: Salim Afiune <afiune@chef.io>

.gitignore

@@ -17,3 +17,6 @@ tmp/
 /omnibus/Berksfile.lock
 /omnibus/Gemfile.lock
 cookbooks/delivery_rust/Berksfile.lock
+
+# Habitat
+results/

plan.sh

@@ -0,0 +1,80 @@
+pkg_name=delivery-cli
+pkg_origin=chef
+pkg_version=0.0.1
+pkg_maintainer="Salim Afiune <afiune@chef.io>"
+pkg_license=('Apache-2.0')
+pkg_source=nosuchfile.tar.gz
+# (Salim) TODO: We want the result to be a portable, static binary
+# in a zero-dependency package. At the moment I cound't make it to
+# compile because we need to figure out how to tell zlib that we are
+# building in static mode, so for now we are packaging the dependencies.
+pkg_deps=(
+  core/gcc
+  core/zlib-musl
+  core/openssl-musl
+)
+pkg_build_deps=(
+  core/musl
+  core/zlib-musl
+  core/openssl-musl
+  core/coreutils
+  core/rust core/gcc
+)
+pkg_bin_dirs=(bin)
+
+# Name of the resulting binary
+_bin="delivery"
+
+do_prepare() {
+  # Can be either `--release` or `--debug` to determine cargo build strategy
+  build_type="--release"
+  build_line "Building artifacts with \`${build_type#--}' mode"
+
+  # Used by Cargo to use a pristine, isolated directory for all compilation
+  export CARGO_TARGET_DIR="$HAB_CACHE_SRC_PATH/$pkg_dirname"
+  build_line "Setting CARGO_TARGET_DIR=$CARGO_TARGET_DIR"
+
+  export rustc_target="x86_64-unknown-linux-musl"
+  build_line "Setting rustc_target=$rustc_target"
+
+  export OPENSSL_LIB_DIR=$(pkg_path_for openssl-musl)/lib
+  export OPENSSL_INCLUDE_DIR=$(pkg_path_for openssl-musl)/include
+  export OPENSSL_STATIC=true
+
+  rustflags="-L$(pkg_path_for zlib-musl)/lib -lz"
+  rustflags="$rustflags -L$(pkg_path_for openssl-musl)/lib -lssl -lcrypto"
+  export RUSTFLAGS="$rustflags"
+
+  export LD_LIBRARY_PATH=$(pkg_path_for gcc)/lib
+  build_line "Setting LD_LIBRARY_PATH=$LD_LIBRARY_PATH"
+}
+
+do_build() {
+  pushd "$PLAN_CONTEXT" > /dev/null
+  cargo build ${build_type#--debug} --target=$rustc_target --verbose
+  popd > /dev/null
+}
+
+do_install() {
+  install -v -D $CARGO_TARGET_DIR/$rustc_target/${build_type#--}/$_bin \
+    $pkg_prefix/bin/$_bin
+}
+
+do_strip() {
+  if [[ "$build_type" != "--debug" ]]; then
+    do_default_strip
+  fi
+}
+
+# Turn the remaining default phases into no-ops
+do_download() {
+  return 0
+}
+
+do_verify() {
+  return 0
+}
+
+do_unpack() {
+  return 0
+}