fix: disable dynamic stack growth when VM flag is disabled

src/userprog/Make.vars

@@ -1,7 +1,7 @@
 # -*- makefile -*-
 
 kernel.bin: DEFINES = -DUSERPROG -DFILESYS
-KERNEL_SUBDIRS = threads devices lib lib/kernel userprog filesys vm
+KERNEL_SUBDIRS = threads devices lib lib/kernel userprog filesys
 TEST_SUBDIRS = tests/userprog tests/userprog/no-vm tests/filesys/base
 GRADING_FILE = $(SRCDIR)/tests/userprog/Grading
 SIMULATOR = --qemu

src/userprog/exception.c

@@ -146,6 +146,7 @@ page_fault (struct intr_frame *f)
   write = (f->error_code & PF_W) != 0;
   user = (f->error_code & PF_U) != 0;
 
+#ifdef VM
   if (user && not_present)
     {
       if (handle_stack_fault (fault_addr, f->esp))
@@ -160,6 +161,7 @@ page_fault (struct intr_frame *f)
       f->eax = 0xffffffff;
       return;
     }
+#endif
 
   /* To implement virtual memory, delete the rest of the function
      body, and replace it with code that brings in the page to