Don't include engine.h when OPENSSL_NO_ENGINE is defined

Fedora 41 and RHEL 10 are deprecating and phasing out OpenSSL ENGINE
support. Downstream has moved `openssl/engine.h` into a separate RPM
package and is recompiling packages with `-DOPENSSL_NO_ENGINE=1`. The
compiler flag disables PyCA cryptography's ENGINE support successfully.
We also like to build the downstream package without the `engine.h`
header file present.

This commit makes the include conditional. The `ENGINE` type is
defined in `openssl/types.h`.

See: https://src.fedoraproject.org/rpms/openssl/c/e67e9d9c40cd2cb9547e539c658e2b63f2736762?branch=rawhide
See: https://issues.redhat.com/browse/RHEL-33747
Signed-off-by: Christian Heimes <christian@python.org>

src/_cffi_src/openssl/engine.py

@@ -5,7 +5,12 @@
 from __future__ import annotations
 
 INCLUDES = """
+#ifdef OPENSSL_NO_ENGINE
+// for ENGINE type
+#include <openssl/types.h>
+#else
 #include <openssl/engine.h>
+#endif
 """
 
 TYPES = """