Fix libunix dependency on OS X

Fixes #261.

--
MOS_MIGRATED_REVID=96967085
diff --git a/src/BUILD b/src/BUILD
index e5957de..9397380 100644
--- a/src/BUILD
+++ b/src/BUILD
@@ -9,7 +9,10 @@
         ":darwin": ["//src/main/native:libunix.dylib"],
         "//conditions:default": ["//src/main/native:libunix.so"],
     }),
-    visibility = ["//src/test/java:__pkg__"],
+    visibility = [
+        "//src/main/java/com/google/devtools/build/workspace:__pkg__",
+        "//src/test/java:__pkg__",
+    ],
 )
 
 genrule(
diff --git a/src/main/java/com/google/devtools/build/workspace/BUILD b/src/main/java/com/google/devtools/build/workspace/BUILD
index 919b431..fc8e161 100644
--- a/src/main/java/com/google/devtools/build/workspace/BUILD
+++ b/src/main/java/com/google/devtools/build/workspace/BUILD
@@ -4,6 +4,10 @@
         "GenerateWorkspace.java",
         "GenerateWorkspaceOptions.java",
     ],
+    data = [
+        "//src:libunix",
+    ],
+    jvm_flags = ["-Djava.library.path=$(GENDIR)/src/main/native"],
     main_class = "com.google.devtools.build.workspace.GenerateWorkspace",
     visibility = ["//visibility:public"],
     deps = [