Make it possible to define data alignment

cranelift/module/src/backend.rs

@@ -59,7 +59,7 @@ where
     fn declare_function(&mut self, name: &str, linkage: Linkage);
 
     /// Declare a data object.
-    fn declare_data(&mut self, name: &str, linkage: Linkage, writable: bool);
+    fn declare_data(&mut self, name: &str, linkage: Linkage, writable: bool, align: Option<u8>);
 
     /// Define a function, producing the function body from the given `Context`.
     ///
@@ -79,6 +79,7 @@ where
         &mut self,
         name: &str,
         writable: bool,
+        align: Option<u8>,
         data_ctx: &DataContext,
         namespace: &ModuleNamespace<Self>,
     ) -> ModuleResult<Self::CompiledData>;