m/n/core: mount efivars

We will need them for lots of upcoming things, let's mount them
so things which need them can use them.

Change-Id: I4417c370615da154bc7cb8b8804cb268d0fd617e
Reviewed-on: https://review.monogon.dev/c/monogon/+/405
Reviewed-by: Mateusz Zalega <mateusz@monogon.tech>
diff --git a/metropolis/node/core/mounts.go b/metropolis/node/core/mounts.go
index f8f0dae..bb98462 100644
--- a/metropolis/node/core/mounts.go
+++ b/metropolis/node/core/mounts.go
@@ -39,6 +39,7 @@
 	}{
 		{"/sys", "sysfs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
 		{"/sys/kernel/tracing", "tracefs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
+		{"/sys/firmware/efi/efivars", "efivarfs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
 		{"/proc", "proc", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
 		{"/dev", "devtmpfs", unix.MS_NOEXEC | unix.MS_NOSUID},
 		{"/dev/pts", "devpts", unix.MS_NOEXEC | unix.MS_NOSUID},