KNOWN_BUGS: cannot enable LDAPS on Windows with cmake

Reported-by: Jack Boos Yu
Closes #6284

docs/KNOWN_BUGS

@@ -139,6 +139,7 @@ problems may have been fixed or changed somewhat since this was written!
  15.9 cert paths autodetected when cross-compiling
  15.10 libspsl is not supported
  15.11 ExternalProject_Add does not set CURL_CA_PATH
+ 15.12 cannot enable LDAPS on Windows
 
  16. Applications
  16.1 pulseUI VPN client
@@ -985,6 +986,10 @@ problems may have been fixed or changed somewhat since this was written!
 
  See https://github.com/curl/curl/issues/6313
 
+15.12 cannot enable LDAPS on Windows
+
+ See https://github.com/curl/curl/issues/6284
+
 16. Applications
 
 16.1 pulseUI VPN client