rusticl: allow asahi to be enabled by default

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31589>

meson_options.txt

@@ -163,7 +163,7 @@ option(
 option(
   'gallium-rusticl-enable-drivers',
   type : 'array',
-  value : ['auto'],
+  value : ['auto', 'asahi'],
   description : 'List of gallium drivers for which rusticl will be enabled ' +
                 'by default',
 )

src/gallium/frontends/rusticl/mesa/pipe/device.rs

@@ -56,7 +56,10 @@ fn get_enabled_devs() -> HashMap<String, u32> {
     let mut res = HashMap::new();
 
     // we require the type here as this list can be empty depending on the build options
-    let default_devs: &[&str] = &[];
+    let default_devs: &[&str] = &[
+        #[cfg(any(rusticl_enable_asahi, rusticl_enable_auto))]
+        "asahi",
+    ];
 
     // I wished we could use different iterators, but that's not really working out.
     let enabled_devs = env::var("RUSTICL_ENABLE").unwrap_or(default_devs.join(","));