[PGPRO-5750] fix windows compilation problem with PG-14

this is caused by upstream commit https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=bed90759fcbcd72d4d06969eebab81e47326f9a2
Reported by Victor Wagner and fixed by Victor Spirin

Author: kulaginm

Diff for: src/utils/file.c

@@ -1,8 +1,10 @@
 #include <stdio.h>
 #include <unistd.h>
-#include <sys/stat.h>
 
 #include "pg_probackup.h"
+/* sys/stat.h must be included after pg_probackup.h (see problems with compilation for windows described in PGPRO-5750) */
+#include <sys/stat.h>
+
 #include "file.h"
 #include "storage/checksum.h"