Move j2objc helper scripts into open-source Bazel.

--
MOS_MIGRATED_REVID=100490916

tools/BUILD

diff --git a/tools/BUILD b/tools/BUILD
index 4aa82c9..8e1ea84 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -12,6 +12,7 @@
         "//tools/jdk:srcs",
         "//tools/genrule:srcs",
         "//tools/cpp:srcs",
+        "//tools/j2objc:srcs",
         "//tools/objc:srcs",
         "//tools/test:srcs",
         "//tools/python:srcs",
@@ -26,6 +27,7 @@
         "//tools/jdk:package-srcs",
         "//tools/genrule:srcs",
         "//tools/cpp:srcs",
+        "//tools/j2objc:srcs",
         "//tools/objc:srcs",
         "//tools/test:srcs",
         "//tools/python:srcs",