Log guest errors in Qemu

This does not seem to actually log a simple int3 from the restricted
kernel wrapper, but it may be that the issue is on the guest; I think
this is worth enabling in Qemu regardless.

Bug: 355609624
Change-Id: I4a05e5a58345223dfbf6aad16bec2b6b166c3a4b

oak_launcher_utils/src/launcher.rs

@@ -127,6 +127,8 @@ impl Instance {
 
         // Construct the command-line arguments for `qemu`.
         cmd.arg("-enable-kvm");
+        // Log guest errors and other interesting events to stderr.
+        cmd.args(["-d", "int,unimp,guest_errors"]);
         // Needed to expose advanced CPU features. Specifically RDRAND which is required
         // for remote attestation.
         cmd.args(["-cpu", "IvyBridge-IBRS,enforce"]);