Make accessFilter file registration thread safe

Author: dnestoro

common/utils/src/main/java/org/graalvm/buildtools/agent/AgentConfiguration.java

@@ -40,14 +40,10 @@
  */
 package org.graalvm.buildtools.agent;
 
-import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.Serializable;
-import java.nio.file.CopyOption;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.StandardCopyOption;
+import java.nio.file.*;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -151,16 +147,18 @@ private void addDefaultAccessFilter() {
         }
 
         try(InputStream accessFilter = AgentConfiguration.class.getResourceAsStream(DEFAULT_ACCESS_FILTER_FILE)) {
-            if (accessFilter != null) {
-                if (!Files.exists(agentDir)) {
-                    Files.createDirectory(agentDir);
-                }
-
-                Files.copy(accessFilter, accessFilterFile, StandardCopyOption.REPLACE_EXISTING);
-                accessFilterFiles.add(accessFilterFile.toString());
-            } else {
+            if (accessFilter == null) {
                 throw new IOException("Cannot find access-filter.json on default location: " + DEFAULT_ACCESS_FILTER_FILE);
             }
+
+            try {
+                Files.createDirectory(agentDir);
+            } catch (FileAlreadyExistsException e) {
+                System.out.println("Agent directory already exists probably because other thread or process created it.");
+            }
+
+            Files.copy(accessFilter, accessFilterFile, StandardCopyOption.REPLACE_EXISTING);
+            accessFilterFiles.add(accessFilterFile.toString());
         } catch (IOException e) {
             throw new RuntimeException("Cannot add default access-filter.json" ,e);
         }