Fix missing include in CRT.c (sys/stat.h)

Include `<sys/stat.h>` for the umask(2) call.
This used to be included indirectly through Compat.h until the
commit 3956cff that refactored
Compat.h.

Build error is reproducible in macOS Tahoe 26.1.

Author: Explorer09

CRT.c

@@ -19,6 +19,7 @@ in the source distribution for its full text.
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/stat.h> // IWYU pragma: keep
 
 #include "CommandLine.h"
 #include "ProvideCurses.h"