RFR: Use os::malloc instead of malloc [v2]

[William Kemper]

On Tue, 2 Aug 2022 22:53:24 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This fixes a compiler error with gcc-10.3.0 used by github actions
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update another use of global malloc/free

I'm closing this PR in favor of a [new PR](https://github.com/openjdk/shenandoah/pull/160) which address the original build issue and another, latent issue in verification of the remembered set.

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PR: https://git.openjdk.org/shenandoah/pull/155