[crac] RFR: 8353243: [CRaC] Show all options in engine help [v2]

[Timofei Pushkin]

On Mon, 7 Apr 2025 11:55:28 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

> I might have focused too much on this being "handy", but my main objective was to not have any code in JVM that would treat different engines differently.

Well, JVM will treat `crexec` somewhat specially anyway because this is the only engine that is not requested by the user directly but rather by the JVM (when it finds that the user requested an executable engine), but I get it that you want to reduce such special handling as much as possible.

> Btw. there's third option: we could use the dladdr/GetModuleFileName in crexec and drop exec_location completely.

Through `dladdr`/`GetModuleFileName` crexec can find where it is located, i.e. this is indeed a substitution for `library_path`. But we'll still need to pass the location of the engine executable because it can be any user-provided absolute path, not only `lib` within JDK installation. The most convenient way would be to use an option which leads us to `exec_location` again.

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PR Review Comment: https://git.openjdk.org/crac/pull/220#discussion_r2031144476