RFR: 8259252: Shenandoah: Shenandoah build failed on AArch64 after JDK-8258459

[Aleksey Shipilev]

On Tue, 5 Jan 2021 17:57:47 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Please review this trivial change that fixes build failure after JDK-8258459

Looks good. `shenandoahBarrierSetC1_x86.cpp` already has this include.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1946