8264485: build.tools.depend.Depend.toString(byte[]) creates malformed hex strings

Reviewed-by: jlahoda

Author: asotona

make/jdk/src/classes/build/tools/depend/Depend.java

@@ -37,6 +37,7 @@
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.HexFormat;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -156,13 +157,7 @@ public void finished(TaskEvent te) {
     }
 
     private String toString(byte[] digest) {
-        StringBuilder result = new StringBuilder();
-
-        for (byte b : digest) {
-            result.append(String.format("%X", b));
-        }
-
-        return result.toString();
+        return HexFormat.of().withUpperCase().formatHex(digest);
     }
 
     private static final class APIVisitor implements ElementVisitor<Void, Void>,