Add Haskell plugin to contrib/release_packages.sh

I forgot to add an entry in `contrib/release_package.sh` as part of the Haskell plugin, so this includes the relevant entry.

Note that this only performs a `compile` step instead of `test` because the first iteration of the plugin only includes the `compile` goal.  Once I add the `test` goal in the next review board then I will update this script to use `test` instead.

Testing Done:
$ ./build-support/bin/release.sh -n  # Passes

Link to travis: https://travis-ci.org/pantsbuild/pants/builds/94242231

Bugs closed: 2649

Reviewed at https://rbcommons.com/s/twitter/r/3198/

contrib/release_packages.sh

@@ -61,6 +61,19 @@ function pkg_go_install_test() {
       test.go contrib/go/examples::
 }
 
+# TODO (ggonzalez): Change the `compile.stack-build` goal to `test.stack-test`
+# once the Haskell plugins adds support for the `test` goal.
+PKG_HASKELL=(
+  "pantsbuild.pants.contrib.haskell"
+  "//contrib/haskell/src/python/pants/contrib/haskell:plugin"
+  "pkg_haskell_install_test"
+)
+function pkg_haskell_install_test() {
+  execute_packaged_pants_with_internal_backends \
+      --plugins="['pantsbuild.pants.contrib.haskell==$(local_version)']" \
+      compile.stack-build contrib/haskell/examples::
+}
+
 PKG_NODE=(
   "pantsbuild.pants.contrib.node"
   "//contrib/node/src/python/pants/contrib/node:plugin"
@@ -97,6 +110,7 @@ CONTRIB_PACKAGES=(
   PKG_BUILDGEN
   PKG_SPINDLE
   PKG_GO
+  PKG_HASKELL
   PKG_NODE
   PKG_PYTHON_CHECKS
 )