No, OpenBSD's implementation of POSIX semaphore is different to NetBSD.
(It doesn't support PSHARED=1.)

Possibly, it is related to the NetBSD failure of T8065.
If importing the secret key fails (which invokes gpg-agent), decryption cannot be succeeded.
I will check OpenBSD implementation of POSIX semaphore, if it's similar to NetBSD one.

Investigating GNU ld, I learned that there is no easy way (~= no way) to suppress the warnings (other than 2>/dev/null). It was implemented by the special section named gnu.warning.SYM where SYM is a symbol. I think that this is not-so-good for glibc to notify its users about possible static link problem, by gnu.warning.SYM.

I found two issues in libgpg-error for spawning functions.

POSIX documentation never says that PSHARED=0 prevents sharing among processes. In my opinion, it still conforms to POSIX even when a PSHARED=0 semaphore can be shared between parent and child processes.

In tests/migrations, (unlike tests/openpgp and tests/cms), the tests do not prepare gpg-agent, but it is gpg which invokes gpg-agent if needed.
Because of that, on NetBSD (where POSIX semaphore has a different semantics), it hangs with gpg --list-secret-key, when gpg tries to spawn the gpg-agent process.
In the old code of 2.4, it simply ignore the npth_protect and npth_unprotect when calling fork to spawn a process.
New code in libgpg-error cares about npth_protect and npth_unprotect but it was not sufficient; We need to care about NetBSD's semantics. Child process should not call npth_protect. With shared semantics, child process's calling npth_protect affects to cause parent process: it hangs.

@wiz Thank you for your quick feedback.

Thank you for the log.