Bazel client: make some libraries visible to ijar 

Ijar will use Bazel's file handling logic so that
we don't have to maintain two implementations, and
don't have to copy this code to implement the
Windows/MSVC code path in
third_party/ijar/platform_utils.cc.

See https://github.com/bazelbuild/bazel/issues/2157

--
Change-Id: Iec327febb882aeaabae55216d0d06488f7c151ed
Reviewed-on: https://cr.bazel.build/9068
PiperOrigin-RevId: 148770951
MOS_MIGRATED_REVID=148770951
diff --git a/src/main/cpp/util/BUILD b/src/main/cpp/util/BUILD
index b5c7b79..2b821a7 100644
--- a/src/main/cpp/util/BUILD
+++ b/src/main/cpp/util/BUILD
@@ -1,5 +1,11 @@
 # Description:
 #   C++ utility source for Bazel
+package_group(
+    name = "ijar",
+    packages = [
+        "//third_party/ijar/...",
+    ],
+)
 
 cc_library(
     name = "util",
@@ -41,6 +47,7 @@
         "file_platform.h",
     ],
     visibility = [
+        ":ijar",
         "//src/test/cpp/util:__pkg__",
         "//src/tools/singlejar:__pkg__",
     ],
@@ -63,7 +70,10 @@
         "//conditions:default": ["errors_posix.cc"],
     }),
     hdrs = ["errors.h"],
-    visibility = ["//src/main/cpp:__subpackages__"],
+    visibility = [
+        ":ijar",
+        "//src/main/cpp:__subpackages__",
+    ],
     deps = [":port"],
 )