RFR: 8351606: Use build_platform for graphviz dependency

[Mikael Vidstedt]

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]

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Commit messages:
 - 8351606: Use build_platform for graphviz dependency

Changes: https://git.openjdk.org/jdk/pull/23976/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23976&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351606
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23976.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23976/head:pull/23976

PR: https://git.openjdk.org/jdk/pull/23976