Allow the openSTA submodule to see the readline initialization.

Thus, it can use it as prepared in
The-OpenROAD-Project/OpenSTA#341

Signed-off-by: Henner Zeller <h.zeller@acm.org>

Author: hzeller

BUILD.bazel

@@ -164,6 +164,7 @@ cc_library(
     name = "tcl_readline_setup",
     srcs = ["src/tcl_readline_setup.cc"],
     hdrs = ["src/tcl_readline_setup.h"],
+    visibility = ["//src/sta:__pkg__"],
     deps = [
         "@tcl_lang//:tcl",
         # tclreadline: provides ENABLE_READLINE define + links libtclreadline.