RFR: 8351606: Use build_platform for graphviz dependency

[Erik Joelsson]

On Mon, 10 Mar 2025 23:37:39 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> Background (from JBS):
> 
> graphviz is run during the build, and needs the build_platform variant rather than target_platform.
> 
> Testing:
> 
> tier1,builds-tier[2-5]

Marked as reviewed by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/23976#pullrequestreview-2675091265