MDEV-23926: Follow-up patch to cleanup plugin/auth_pam/CMakeLists.txt code

This patch moves definitions of macros variables
   HAVE_PAM_SYSLOG, HAVE_PAM_EXT_H, HAVE_PAM_APPL_H, HAVE_STRNDUP
from command line (in the form -Dmacros) to the auto-generated
header file config_auth_pam.h

plugin/auth_pam/CMakeLists.txt

@@ -33,19 +33,7 @@ SET(CMAKE_REQUIRED_LIBRARIES pam)
 CHECK_FUNCTION_EXISTS(pam_syslog HAVE_PAM_SYSLOG)
 SET(CMAKE_REQUIRED_LIBRARIES)
 
-IF(HAVE_PAM_SYSLOG)
-  ADD_DEFINITIONS(-DHAVE_PAM_SYSLOG)
-ENDIF()
-
-IF(HAVE_PAM_EXT_H)
-  ADD_DEFINITIONS(-DHAVE_PAM_EXT_H)
-ENDIF()
-
 IF(HAVE_PAM_APPL_H)
-  ADD_DEFINITIONS(-DHAVE_PAM_APPL_H)
-  IF(HAVE_STRNDUP)
-    ADD_DEFINITIONS(-DHAVE_STRNDUP)
-  ENDIF(HAVE_STRNDUP)
   FIND_LIBRARY(PAM_LIBRARY pam) # for srpm build-depends detection
   MYSQL_ADD_PLUGIN(auth_pam auth_pam.c LINK_LIBRARIES pam MODULE_ONLY)
 

plugin/auth_pam/auth_pam.c

@@ -16,6 +16,7 @@
 
 #define _GNU_SOURCE 1 /* for strndup */
 
+#include <config_auth_pam.h>
 #include <mysql/plugin_auth.h>
 #include <stdio.h>
 #include <string.h>