kerberos: Fix numerous segfaults when using weak crypto

Weak crypto is provided by the openssl legacy provider which is
not load by default. Load the legacy providers as needed.

When the legacy provider is loaded into the default context the default
provider will no longer be automatically loaded. Without the default
provider the various kerberos applicaions and functions will abort().

This is the second attempt at this patch. Instead of linking
secure/lib/libcrypto at build time we now link it at runtime, avoiding
buildworld failures under Linux and MacOS. This is because
TARGET_ENDIANNESS is undefined at pre-build time.

PR: 272835
MFC after: 3 days
X-MFC: only to stable/14
Tested by: netchild
Joerg Pulz <Joerg.Pulz@frm2.tum.de> (previous version)

Revert "kerberos: Fix numerous segfaults when using weak crypto"

This revision breaks Linux and MacOS cross builds because
TARGET_ENDIANNESS is not define during bootstrapping on these
platforms.

I think the correct approach would be to separate the new
fbsd_ossl_provider_load() and unload functions into their own
library (instead of libroken). This avoids the less desirable
option of including bsd.cpu.mk in secure/lib/Makefile.common,
which does build but could complicate future work.

Reported by: jrtc27

This reverts commit cb350ba7bf7ca7c4cb97ed2c20ab45af60382cfb.

kerberos: Fix numerous segfaults when using weak crypto

Weak crypto is provided by the openssl legacy provider which is
not load by default. Load the legacy providers as needed.

When the legacy provider is loaded into the default context the default
provider will no longer be automatically loaded. Without the default
provider the various kerberos applicaions and functions will abort().

PR: 272835
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D43009
Tested by: netchild, Joerg Pulz <Joerg.Pulz@frm2.tum.de>