fix(shim-sev): guard unused imports with `cfg`
Some imports are only used in `feature = dbg`.
@@ -7,8 +7,9 @@ use crate::spin::{Locked, RacyCell};
use core::arch::asm;
use core::mem::size_of;
-use libc::{SYS_write, STDERR_FILENO, STDOUT_FILENO};
+#[cfg(feature = "dbg")]
+use libc::{SYS_write, STDERR_FILENO, STDOUT_FILENO};
use sallyport::guest;
use sallyport::guest::Handler;
use sallyport::item::enarxcall::SYS_GETATT;
