Make libvda-stub the default

libvda is only used on ChromeOS, which compiles with
--no-default-features.

Even though libvda may not be enabled by default, it is still
part of the workspace and will be compiled (and fail without
libvda-stub).

This enables crosvm builds with the default feature set on plain
linux.

BUG=b:266129169
TEST=cargo nextest run --workspace

Change-Id: I521bb5e715852aa6be69484db04e2cf4dbc3684e
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4235223
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Auto-Submit: Dennis Kempin <denniskempin@google.com>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
diff --git a/Cargo.toml b/Cargo.toml
index c46a217..7b3bc48 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -119,7 +119,7 @@
 
 [features]
 ## Default features of crosvm. This selection is somewhat arbitrary for historical reasons.
-default = ["audio", "balloon", "config-file", "document-features", "gpu", "qcow", "usb"]
+default = ["audio", "balloon", "config-file", "document-features", "gpu", "qcow", "usb", "libvda-stub"]
 
 ## Enables support for the Android [sparse image format](https://android.googlesource.com/platform/system/core/+/HEAD/libsparse/sparse_format.h)
 ## in the block device.