asn1: conditionalize V_ASN1_APP_CHOOSE for LibreSSL

[mischief]

Description

this was removed in
openbsd/src@44d602d.

unbreak the build by making it conditional on LIBRESSL_VERSION_NUMBER.

Related Issue

N/A

Type of Change

• Bug fix
• New feature
• Documentation update
• Code review/analysis
• Performance improvement
• Code refactoring
• Other (please describe)

Changes Made

Please list the specific changes made in this PR:

Testing

Please describe the tests you ran to verify your changes:

• Existing tests pass
• Added new tests
• Manual testing performed

i tried to run make test but there are many test failures unrelated to my change to fix the build. probably separate issues can investigate them.

one notable failure is

luajit(17382) in free(): double free 0xe0177e486e0
Abort trap (core dumped)

which should probably be looked at, as it may impact targets other than OpenBSD/LibreSSL as well..

Checklist

• My code follows the style guidelines of this project (clang-format)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

OpenSSL Compatibility

Please indicate which OpenSSL versions were tested (if applicable):

• OpenSSL 1.0.2u
• OpenSSL 1.1.1w
• OpenSSL 3.0.x
• OpenSSL 3.5+
• LibreSSL 3.3.6+

Additional Notes

Add any other context about the pull request here.

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