libarchive: Avoid a build failure with OpenSSL 3.0

[khorben]

Summary

OPENSSL_API_COMPAT was used to specify the OpenSSL 1.1 API version for libarchive (as per https://reviews.freebsd.org/rG5a7500dab9b8480dacd5a9b70bad1541391342e4), preparing for the switch to OpenSSL 3.0. Unfortunately this broke the build with compilers checking for discarded qualifiers, since OpenSSL's OSSL_PARAM_construct_utf8_string() expects a char * but is really fine with string litterals according to EVP_MAC_fetch(3).

This change is a NFC while we're still using OpenSSL 1.1.1 but will avoid deprecation warnings upon the switch to OpenSSL 3.0.

A future update may migrate to use the OpenSSL 3.0 APIs.

PR: 271615
Sponsored by: The FreeBSD Foundation

[emaste]

There's an upstream fix in libarchive although it doesn't look like it will get merged in the short term.

[emaste]

In particular https://github.com/libarchive/libarchive/commit/4ebfd961873310cac894ffd579e4569f369e8990