Fails to build when OpenSSL is build without Certificate Transparency (CT) support

[koobs]

cryptography fails to build with compiler errors when compiled against an OpenSSL that has Certificate Transparency (CT) disabled.

Build warnings/error summary:

• Several: error: use of undeclared identifier 'SCT_*'
• Several: error: use of undeclared identifier 'CT_LOG_*'
• Several: warning: implicit declaration of function 'SCT_*' is invalid in C99
• Final error:

build/temp.freebsd-13.0-CURRENT-amd64-3.7/_openssl.c:33416:8: error: unknown type name 'ct_log_entry_type_t'
static ct_log_entry_type_t _cffi_d_SCT_get_log_entry_type(SCT const * x0)
       ^

Reproduction Environment:

• Operating System: FreeBSD 13.0-CURRENT Document how to contribute private things #3 r354143 (amd64)
  • FreeBSD clang version 9.0.0 (tags/RELEASE_900/final 372316) (based on LLVM 9.0.0)
• OpenSSL: 1.1.1d-freebsd 10 Sep 2019 (via ports, with CT option disabled)
  • ./configure: --openssldir=/usr/local/openssl --prefix=/usr/local no-ct
• Python 2.7.17 / 3.7.5
• cryptography: 2.8 (PyPI sdist)

Full build log attached:

cryptography-2.8-no-CT-build-failure.log

[reaperhulk]

This and #5113 are related in that they're configs we don't support right now and maybe should.

[reaperhulk]

(Closing this to track "unsupported configs" in #5113)