RFR: 8323621: JDK build should exclude snippet class in java.lang.foreign

[Per Minborg]

This PR proposes to remove the snippet files in `java/lang/foreign/snippet-files` from the build.

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Commit messages:
 - Exclude snipet files

Changes: https://git.openjdk.org/jdk/pull/17403/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17403&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323621
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17403.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17403/head:pull/17403

PR: https://git.openjdk.org/jdk/pull/17403