Fix to close the compiler object in scalacinvoker (#1545)

* close compiler object in scalacinvoker
This fixes functionality that was accidently broken in PR#1529

Author: crt-31

src/java/io/bazel/rulesscala/scalac/ScalacInvoker.java

@@ -32,6 +32,8 @@ public static ScalacInvokerResults invokeCompiler(CompileOptions ops, String[] c
       } else {
         throw ex;
       }
+    } finally {
+      comp.close();
     }
 
     results.stopTime = System.currentTimeMillis();