Reduce compiletest code for easier decoupling (rust-lang#694)

* Reduce compiletest code for easier decoupling

* Add modifications copyright

* Remove unused function `get_lib_name`

Author: adpaco-aws

src/tools/compiletest/Cargo.toml

@@ -1,3 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+#
+# Modifications Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# See GitHub history for details.
+
 [package]
 name = "compiletest"
 version = "0.0.0"