Steps to reproduce:

1. Compile Zabbix on a system with OpenSSL installed in a non-standard location (e.g. macOS) and the OpenSSL headers are not available in default include path

Result:

In file included from scripts.c:20:
In file included from ./scripts.h:23:
In file included from ../../../include/zbxcacheconfig.h:24:
../../../include/zbxcomms.h:108:11: fatal error: 'openssl/ssl.h' file not found
#       include <openssl/ssl.h>
                ^~~~~~~~~~~~~~~
1 error generated.

Expected:
Successful compilation.

Analysis:
This happens because now zbxcoms.h includes ssl.h and zbxcoms.h is included in many headers. The corresponding makefiles must point to the correct location of OpenSSL includes.

Please see the patch that fixes this problem: tls_includes.patch