.include directive with relative path should print a warning when OPENSSL_CONF_INCLUDE env. var. is not defined

Hi, try the following commands.

$ touch a.cnf
$ mkdir sub1 && cd $_
$ echo ".include ../a.cnf" > b.cnf
$ mkdir sub2 && cd $_
$ echo ".include ../b.cnf" > c.cnf
$ openssl ca -config ./c.cnf
      (Error messages like the next)
$ openssl ca -config ../b.cnf
Using configuration from ../b.cnf
variable lookup failed for ca::default_ca
4007E9D4017F0000:error:80000002:system library:process_include:No such file or directory:../crypto/conf/conf_def.c:822:calling stat(../a.cnf)
4007E9D4017F0000:error:0700006C:configuration file routines:NCONF_get_string:no value:../crypto/conf/conf_lib.c:315:group=ca name=default_ca

../a.cnf can't be found.

Version: OpenSSL 3.0.15 3 Sep 2024 (Library: OpenSSL 3.0.15 3 Sep 2024)