hack/test-bazel-build-tarball: Pass args through to bazel build

This allows callers to set build options [1] if needed.  The Prow
tests need this to set HOME to avoid [2]:

  ERROR: /home/prow/go/src/github.com/openshift/installer/BUILD.bazel:106:1: error executing shell command: 'bazel-out/host/bin/external/bazel_tools/tools/build_defs/pkg/build_tar --flagfile=bazel-out/k8-fastbuild/bin/tf_bin.args' failed (Exit 1)
  Traceback (most recent call last):
    File "/usr/lib/python2.7/site.py", line 554, in <module>
      main()
    File "/usr/lib/python2.7/site.py", line 536, in main
      known_paths = addusersitepackages(known_paths)
    File "/usr/lib/python2.7/site.py", line 272, in addusersitepackages
      user_site = getusersitepackages()
    File "/usr/lib/python2.7/site.py", line 247, in getusersitepackages
      user_base = getuserbase() # this will also set USER_BASE
    File "/usr/lib/python2.7/site.py", line 237, in getuserbase
      USER_BASE = get_config_var('userbase')
    File "/usr/lib/python2.7/sysconfig.py", line 582, in get_config_var
      return get_config_vars().get(name)
    File "/usr/lib/python2.7/sysconfig.py", line 533, in get_config_vars
      _CONFIG_VARS['userbase'] = _getuserbase()
    File "/usr/lib/python2.7/sysconfig.py", line 210, in _getuserbase
      return env_base if env_base else joinuser("~", ".local")
    File "/usr/lib/python2.7/sysconfig.py", line 196, in joinuser
      return os.path.expanduser(os.path.join(*args))
    File "/usr/lib/python2.7/posixpath.py", line 262, in expanduser
      userhome = pwd.getpwuid(os.getuid()).pw_dir
  KeyError: 'getpwuid(): uid not found: 1000130000'

The chain for that crash is:

1. Bazel invokes build_tar via run_shell with
   use_default_shell_env=True [3], so only environment variables
   declared with --action_env [1] are exposed to build_tar.
2. Python sees $HOME is empty and falls back to
   pwd.getpwuid(os.getuid()).pw_dir [4].
3. OpenShift Prow containers execute with arbitrary container-side
   UIDs [5], so the getpwuid call fails.

With this commit, Prow can setup --action_env to work around its
arbitrary container-side UIDs [6].

[1]: https://docs.bazel.build/versions/master/command-line-reference.html#build-options
[2]: https://storage.googleapis.com/origin-ci-test/pr-logs/pull/openshift_installer/123/ci-pull-openshift-installer-bazel-build-tarball/4/build-log.txt
[3]: https://github.com/bazelbuild/bazel/blob/0.16.1/tools/build_defs/pkg/pkg.bzl#L82-L89
[4]: https://github.com/python/cpython/blob/1f34aece28d143edb94ca202e661364ca394dc8c/Lib/posixpath.py#L260-L262
[5]: openshift/release#1178 (comment)
[6]: openshift/release#1185

hack/test-bazel-build-tarball.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 if [ "$IS_CONTAINER" != "" ]; then
   set -x
-  bazel --output_base=/tmp build tarball
+  bazel --output_base=/tmp build "$@" tarball
 else
   docker run -e IS_CONTAINER='TRUE' --rm -v "$PWD":"$PWD" -v /tmp:/tmp:rw -w "$PWD" quay.io/coreos/tectonic-builder:bazel-v0.3 ./hack/test-bazel-build-tarball.sh
 fi