RFR: 7526: JMC not buildable with jdk17 [v12]

[Johannes Bechberger]

> Tested on Java 11 x86 and aarch64 (azul, but only builds), and on Java 17 x86 and aarch64.

Johannes Bechberger has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Improve GitHub actions

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Changes:
  - all: https://git.openjdk.java.net/jmc/pull/363/files
  - new: https://git.openjdk.java.net/jmc/pull/363/files/a61d516d..53da0254

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=363&range=11
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=363&range=10-11

  Stats: 9 lines in 1 file changed: 2 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jmc/pull/363.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/363/head:pull/363

PR: https://git.openjdk.java.net/jmc/pull/363