Debug build triple-faulting on KVM

[liuw]

Commit 12a3c21

Build with cargo build --target target.json -Zbuild-std=core -Zbuild-std-features=compiler-builtins-mem.

Run the resulting hypervisor-fw binary. It triple-faults.

After digging a bit, the faulting line is

rust-hypervisor-firmware/src/fat.rs

Line 213 in 12a3c21

s.copy_from_slice(unsafe { &lfns[i].name[..] });

0.2.8 debug build is okay.