compile [exe|aot-snapshot] with --no-sound-null-safety does not work when the Dart VM is switched to sound null safety by default

[a-siva]

The compile [exe|aot-snapshot] commands appear to rely on the automatic detection of null safety from the kernel file as a result when the Dart VM is switched to sound null safety by default these commands do not work when used with --no-sound-null-safety

dart compile exe --no-sound-null-safety hello.dart

would fail

[a-siva]

This now works when we retain the ability to detect the null safety mode from the AOT snapshot or the kernel file.