gssapictx.c:681:10: error: implicit declaration of function 'gsskrb5_register_acceptor_identity' on illumos

On OpenIndiana 2020.04 (an illumos distribution) compilation of BIND main commit 78a4ed31 fails in lib/dns/gssapictx.c with:

gssapictx.c: In function 'dst_gssapi_acceptctx':
gssapictx.c:681:10: error: implicit declaration of function 'gsskrb5_register_acceptor_identity' [-Werror=implicit-function-declaration]
   gret = gsskrb5_register_acceptor_identity(gssapi_keytab);
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Perhaps #if defined(ISC_PLATFORM_GSSAPI_KRB5_HEADER) around gsskrb5_register_acceptor_identity() is missing (like v9_16 has)?

--- a/lib/dns/gssapictx.c
+++ b/lib/dns/gssapictx.c
@@ -678,6 +678,7 @@ dst_gssapi_acceptctx(gss_cred_id_t cred, const char *gssapi_keytab,
        }
 
        if (gssapi_keytab != NULL) {
+#if defined(ISC_PLATFORM_GSSAPI_KRB5_HEADER) || defined(WIN32)
                gret = gsskrb5_register_acceptor_identity(gssapi_keytab);
                if (gret != GSS_S_COMPLETE) {
                        gss_log(3,
@@ -687,6 +688,27 @@ dst_gssapi_acceptctx(gss_cred_id_t cred, const char *gssapi_keytab,
                                gss_error_tostring(gret, 0, buf, sizeof(buf)));
                        return (DNS_R_INVALIDTKEY);
                }
+#else  /* if defined(ISC_PLATFORM_GSSAPI_KRB5_HEADER) || defined(WIN32) */
+               /*
+                * Minimize memory leakage by only setting KRB5_KTNAME
+                * if it needs to change.
+                */
+               const char *old = getenv("KRB5_KTNAME");
+               if (old == NULL || strcmp(old, gssapi_keytab) != 0) {
+                       size_t size;
+                       char *kt;
+
+                       size = strlen(gssapi_keytab) + 13;
+                       kt = malloc(size);
+                       if (kt == NULL) {
+                               return (ISC_R_NOMEMORY);
+                       }
+                       snprintf(kt, size, "KRB5_KTNAME=%s", gssapi_keytab);
+                       if (putenv(kt) != 0) {
+                               return (ISC_R_NOMEMORY);
+                       }
+               }
+#endif /* if defined(ISC_PLATFORM_GSSAPI_KRB5_HEADER) || defined(WIN32) */
        }
 
        log_cred(cred);