cc_library linked_statically_by attribute Fails on Relative Label Path

gistfile1.txt

➜  /tmp git clone https://github.com/bmzhao/experimental.git
Cloning into 'experimental'...
remote: Enumerating objects: 10, done.
remote: Counting objects: 100% (10/10), done.
remote: Compressing objects: 100% (7/7), done.
remote: Total 10 (delta 1), reused 10 (delta 1), pack-reused 0
Receiving objects: 100% (10/10), done.
Resolving deltas: 100% (1/1), done.


➜  /tmp cd experimental

➜  experimental git:(master)  bazel build --experimental_cc_shared_library :a_so
Starting local Bazel server and connecting to it...
ERROR: /tmp/experimental/BUILD:11:1: in cc_shared_library rule //:a_so: 
Traceback (most recent call last):
	File "/tmp/experimental/BUILD", line 11
		cc_shared_library(name = 'a_so')
	File "/usr/local/google/home/bmzhao/.cache/bazel/_bazel_bmzhao/c4d400b2a1516530797bd4b776e002bf/external/rules_cc/examples/experimental_cc_shared_library.bzl", line 216, in _cc_shared_library_impl
		_filter_inputs(ctx, <4 more arguments>)
	File "/usr/local/google/home/bmzhao/.cache/bazel/_bazel_bmzhao/c4d400b2a1516530797bd4b776e002bf/external/rules_cc/examples/experimental_cc_shared_library.bzl", line 172, in _filter_inputs
		fail(<1 more arguments>)
We can't link //:a either statically or dynamically
ERROR: Analysis of target '//:a_so' failed; build aborted: Analysis of target '//:a_so' failed; build aborted
INFO: Elapsed time: 3.720s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (14 packages loaded, 48 targets configured)