RFR: 8368674: Incremental builds keep rebuilding interim jmod

[Magnus Ihse Bursie]

After [JDK-8366899](https://bugs.openjdk.org/browse/JDK-8366899), the interim jmods will be constantly rebuilt during incremental builds, triggering a cascade that ends with the entire JDK image being rebuilt.

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Commit messages:
 - 8368674: Incremental builds keep rebuilding interim jmod

Changes: https://git.openjdk.org/jdk/pull/27490/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27490&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368674
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27490.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27490/head:pull/27490

PR: https://git.openjdk.org/jdk/pull/27490