instead of a new panic
For unwinding with SEH, we currently construct a C++ exception with the
panic data. Being a regular C++ exception, it interacts with the C++
exception handling machinery and can be retrieved via
`std::current_exception`, which needs to copy the exception. We can't
support that, so we panic, which throws another exception, which the
C++ runtime tries to copy and store into the exception_ptr, which panics
again, which causes the C++ runtime to store a `bad_exception` instance.
However, this doesn't work because the panics thrown by the copy
function will be dropped without being rethrown, and causes unnecessary
log spam in stderr. Fix this by directly throwing an exception without
data, which doesn't cause log spam and can be dropped without being
rethrown.
96cdbb9ba7