Reapply CL "Option to truncate integers to 64 bits, part 2"

runtime/vm/snapshot_test.cc

Index: runtime/vm/snapshot_test.cc
diff --git a/runtime/vm/snapshot_test.cc b/runtime/vm/snapshot_test.cc
index 3897786ffd189591996e0eed9233c352dfa0f505..0d387862100e1a7f6ca65d1b5264e2d4ded3ff34 100644
--- a/runtime/vm/snapshot_test.cc
+++ b/runtime/vm/snapshot_test.cc
@@ -401,6 +401,9 @@ TEST_CASE(SerializeCapability) {
 }
 
 TEST_CASE(SerializeBigint) {
+  if (Bigint::IsDisabled()) {
+    return;
+  }
   // Write snapshot with object content.
   const char* cstr = "0x270FFFFFFFFFFFFFD8F0";
   const String& str = String::Handle(String::New(cstr));
@@ -473,6 +476,9 @@ void CheckBigint(const char* bigint_value) {
 }
 
 TEST_CASE(SerializeBigint2) {
+  if (Bigint::IsDisabled()) {
+    return;
+  }
   CheckBigint("0x0");
   CheckBigint("0x1");
   CheckBigint("-0x1");