Add clone syscall test

cannon/mipsevm/open_mips_tests/test/clone.asm

+.section .test, "x"
+    .balign 4
+    .set    noreorder
+    .global test
+    .ent    test
+
+test:
+  li $v0, 4120
+  syscall
+  li $t0, 0x1
+  subu $v0, $v0, $t0
+  sltiu $v0, $v0, 1
+
+# save results
+  lui     $s0, 0xbfff         # Load the base address 0xbffffff0
+  ori     $s0, 0xfff0
+  ori     $s1, $0, 1          # Prepare the 'done' status
+
+  sw      $v0, 8($s0)         # Set the test result
+  sw      $s1, 4($s0)         # Set 'done'
+
+$done:
+  jr $ra
+  nop
+
+  .end test