RFR: 8304888: Add dedicated VMProps for linker and fallback linker [v3]

[Alan Bateman]

On Fri, 28 Apr 2023 12:59:26 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> This patch adds a dedicated jtreg property to check which CABI is being used by the JDK, which can be used both to check whether the foreign linker is supported, and whether the fallback linker is being used. (and, possibly it can also be use to check for a particular ABI in case we want to add ABI specific tests).
>> 
>> Checking whether the foreign linker is supported currently requires using an unwieldy expression that checks if we are running on a platform that has a foreign linker port. Checking for the fallback linker currently uses `vm.flavor != "zero"` which is not always correct, since the fallback linker can also be used on other platforms which are not `zero`.
>> 
>> To initialize the property, VMProps directly reads `jdk.internal.foreig.CABI::current()`. Since this class is in an internal package, `--add-exports` flags are added as javac flags and VM flags for the extra prop definitions class.
>
> Jorn Vernee has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 44 commits:
> 
>  - Merge branch 'master' into VMProps
>  - use only jdk.CABI property
>  - use extra props to check for linker
>  - Add fallbackLinker vmprop
>  - Merge pull request #3 from JornVernee/IsForeignLinkerSupported
>    
>    rename has_port
>  - rename has_port
>  - Merge pull request #2 from JornVernee/WSL_BB
>    
>    account for missing functional in WSL in TestByteBuffer
>  - account for missing mincore on WSL in TestByteBuffer
>  - Merge branch 'master' into PR_21_V2
>  - 8305369: Issues in zero-length memory segment javadoc section
>  - ... and 34 more: https://git.openjdk.org/jdk/compare/b827ce83...8a6df30e

Marked as reviewed by alanb (Reviewer).

test/jtreg-ext/requires/VMProps.java line 657:

> 655:         return "" + result;
> 656:     }
> 657: 

It might be useful to add a comment on `cabi()` as it may not be obvious that this is C ABI.

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PR Review: https://git.openjdk.org/jdk/pull/13429#pullrequestreview-1405909218
PR Review Comment: https://git.openjdk.org/jdk/pull/13429#discussion_r1180380624