hg: jdk/sandbox: Fix build error (not all compilers understand zero sized arrays)

[thomas.stuefe at gmail.com]

Changeset: 0ed5fcaedda3
Author:    stuefe
Date:      2020-04-06 12:47 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/0ed5fcaedda3

Fix build error (not all compilers understand zero sized arrays)

! src/hotspot/share/memory/metaspace/allocationGuard.hpp