Update systemc library build file

Remove TODO and specify the cmake build target

Change-Id: Iaff5dfafe695d721ca082db96e205aca6cdfec01

external/systemc.BUILD

diff --git a/external/systemc.BUILD b/external/systemc.BUILD
index 2a48cf8..e43e428 100644
--- a/external/systemc.BUILD
+++ b/external/systemc.BUILD
@@ -1,3 +1,5 @@
+# Copyright 2023 Google LLC
+
 load("@rules_foreign_cc//foreign_cc:defs.bzl", "cmake")
 
 filegroup(
@@ -5,7 +7,6 @@
     srcs = glob(["**"]),
 )
 
-# TODO(derekjchow): Set isystem for systemc headers.
 cmake(
     name = "systemc",
     cache_entries = {
@@ -18,5 +19,6 @@
     install = True,
     lib_source = "@accellera_systemc//:all_srcs",
     out_static_libs = ["libsystemc.a"],
+    targets = ["systemc"],
     visibility = ["//visibility:public"],
 )