properly expose all symbls in manganis without linker intercept (#3230)

* force a volatile read of manganis symbols to preserve them in the final binary

packages/manganis/manganis-macro/src/asset.rs

@@ -104,6 +104,8 @@ impl ToTokens for AssetParser {
 
                         // "/blahcss123.css"
                         bundled: #bundled,
+
+                        metadata: __volatile_reader as fn() -> u8,
                     }
                 }
             ) #option_source

packages/manganis/manganis-macro/src/linker.rs

@@ -17,5 +17,9 @@ pub fn generate_link_section(asset: &impl Serialize) -> TokenStream2 {
         #[link_section = #section_name]
         #[used]
         static ASSET: [u8; #len] = * #asset_bytes;
+
+        fn __volatile_reader() -> u8 {
+            unsafe { std::ptr::read_volatile(ASSET.as_ptr()) }
+        }
     }
 }

packages/manganis/manganis/src/builder.rs

@@ -14,6 +14,9 @@ pub struct Asset {
     ///
     /// `blah-123.css``
     pub bundled: &'static str,
+
+    /// The metadata for this asset plumbed by the compiler
+    pub metadata: fn() -> u8,
 }
 
 impl Asset {
@@ -47,6 +50,9 @@ impl Asset {
     /// Attempts to resolve it against an `assets` folder in the current directory.
     /// If that doesn't exist, it will resolve against the cargo manifest dir
     pub fn resolve(&self) -> PathBuf {
+        // Force a volatile read of the metadata to ensure the symbol makes it into the binary
+        (self.metadata)();
+
         // If the asset is relative, we resolve the asset at the current directory
         if !dioxus_core_types::is_bundled_app() {
             return PathBuf::from(self.local);