[win/signal] Disable ctrl-c handling in the parent dartdev process.

Ensure that ctrl-c is handled by spawned dartvm.exe process, parent dart.exe does not get in a way of handling ctrl-c, exits only after spawned dartvm.exe exits.

Fixes #61399
TEST=manually on windows

Change-Id: Ibdbfbb5e4863c76bbbf2e30fb2d94f72a2676d4a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/446704
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Alexander Aprelev <[email protected]>

Author: aam

runtime/bin/process_win.cc

@@ -1042,6 +1042,8 @@ int Process::Exec(Namespace* namespc,
   // Now wait for this child process to terminate (normal exit or crash).
   HANDLE child_process = starter.child_process_handle_;
   ASSERT(child_process != INVALID_HANDLE_VALUE);
+  // Don't attempt to handle ctrl-c events, let spawned child handle them.
+  SetConsoleCtrlHandler(NULL, TRUE);
   DWORD wait_result = WaitForSingleObject(child_process, INFINITE);
   if (wait_result != WAIT_OBJECT_0) {
     BufferFormatter f(errmsg, errmsg_len);