diff -r 14e098407bb0 -r ad69fd32778e src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java	Mon Oct 21 15:11:44 2019 +0200
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java	Mon Oct 21 15:38:26 2019 +0200
@@ -44,6 +44,7 @@
 import java.nio.file.Path;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Objects;
@@ -173,6 +174,10 @@
     private long lastUsedTime = System.currentTimeMillis();
     protected long deferredCloseTimeout = 0;
 
+    public void clear() {
+        new HashSet<>(options.keySet()).forEach(k -> options.remove(k));
+    }
+
     protected ClassLoader getClassLoader(URL[] urls) {
         ClassLoader thisClassLoader = getClass().getClassLoader();