IBMi build broken due to missing realpath()

[andrewkirillov-ibm]

I did this

Compile 8.12.0 on IBM i V7R4M0 system, with SSL enabled. Got the following errors:

CZM1001:  VLS_SCACHE__819.c, 367.23: CZM0304(10) No function prototype given for "realpath".
CZM1003:  VLS_SCACHE__819.c, 367.21: CZM0196(30) Initialization between types "char*" and "int" is not allowed.
..
CZS0601:  Module VLS_SCACHE is not created because statement errors occurred.

The issue is introduced by the following commit:
fa0ccd9

Here lib/vtls/vtls_scache.c was introduced, which uses _fullpath() on Windows and realpath() on all other platforms. IBMi system header, however, do not provide realpath() or its replacement.

I expected the following

Clean build

curl/libcurl version

8.12.0

operating system

OS400 V7R4M0

[andrewkirillov-ibm]

As IBMi does not provide realpath() or a replacement for it, a fix could be to change #ifdefs

From

#ifdef _WIN32
#else
#endif

to

#ifdef _WIN32
#elif !defined(__OS400__)
#endif

It will the fall back to return Curl_dyn_addf(buf, ":%s-%s", name, path); by default.