feat(tvix/eval): thread codemap through to disassembler

If the disassembler feature is enabled, make sure that an Rc of the
codemap is available through the chunk.

Change-Id: I700f27ab665a704f73457b19bd2d7efc93828a16
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6414
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

tvix/eval/src/chunk.rs

@@ -26,6 +26,9 @@ pub struct Chunk {
     pub code: Vec<OpCode>,
     pub constants: Vec<Value>,
     spans: Vec<SourceSpan>,
+
+    #[cfg(feature = "disassembler")]
+    pub codemap: std::rc::Rc<codemap::CodeMap>,
 }
 
 impl Chunk {