RFR: 8343345: Use -jvmArgsPrepend when running microbenchmarks in RunTests.gmk

[Magnus Ihse Bursie]

On Thu, 31 Oct 2024 08:53:07 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> Update RunTests.gmk to use `-jvmArgsPrepend` to avoid overwriting built-in micro `jvmArgs` flags.

Marked as reviewed by ihse (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/21800#pullrequestreview-2409050109