Revert "implement immutable variables codegen"

This reverts commit 0e6a6d12c3.

crates/llvm-context/src/polkavm/context/global.rs

@@ -51,31 +51,4 @@ impl<'ctx> Global<'ctx> {
 
         global
     }
-
-    /// Construct an external global.
-    pub fn declare<D, T>(
-        context: &mut Context<'ctx, D>,
-        r#type: T,
-        address_space: AddressSpace,
-        name: &str,
-    ) -> Self
-    where
-        D: PolkaVMDependency + Clone,
-        T: BasicType<'ctx>,
-    {
-        let r#type = r#type.as_basic_type_enum();
-
-        let value = context
-            .module()
-            .add_global(r#type, Some(address_space.into()), name);
-        let global = Self { r#type, value };
-
-        global.value.set_linkage(inkwell::module::Linkage::External);
-        global
-            .value
-            .set_visibility(inkwell::GlobalVisibility::Default);
-        global.value.set_externally_initialized(true);
-
-        global
-    }
 }