Make constant_propagation_08 test platform agnostic

We had a varying number of simplifications as platforms with sizeof(int)
!= sizeof(ssize_t) would yield 2 simplifications, and those with
matching bit widths only a single one. The extra simplification referred
to the cast in the index operand (on platforms with sizeof(int) !=
sizeof(ssize_t)), which we can avoid by making the index a long-type
constant in the first place.

Author: tautschnig

regression/goto-analyzer/constant_propagation_08/main.c

@@ -5,10 +5,17 @@ int main()
   int i;
   i = 0;
 
+#ifndef _WIN64
   if (i==0)
-    a[0]=1;
+    a[0l] = 1;
   else
-    a[1]=2;
+    a[1l] = 2;
+#else
+  if(i == 0)
+    a[0ll] = 1;
+  else
+    a[1ll] = 2;
+#endif
 
   __CPROVER_assert(a[0] == 1 || a[1] == 2, "a[0]==1 || a[1]==2");
 

regression/goto-analyzer/constant_propagation_08/test-vsd.desc

@@ -3,7 +3,7 @@ main.c
 --variable-sensitivity --vsd-arrays every-element --simplify out.gb
 ^EXIT=0$
 ^SIGNAL=0$
-^Simplified:  assert: 1, assume: 0, goto: 1, assigns: [12], function calls: 0$
-^Unmodified:  assert: 0, assume: 0, goto: 2, assigns: [89], function calls: 2$
+^Simplified:  assert: 1, assume: 0, goto: 1, assigns: 1, function calls: 0$
+^Unmodified:  assert: 0, assume: 0, goto: 2, assigns: 9, function calls: 2$
 --
 ^warning: ignoring