Include symtab2gb conversion in --only-codegen (#1585)

#957 will need more fixes and discussions to be enabled. In the meantime, this PR includes the symtab2gb conversion step in --only-codegen runs, so that Kani fails if the conversion from Kani-generated symbol tables to GotoC program is invalid.

kani-driver/src/main.rs

@@ -40,14 +40,16 @@ fn cargokani_main(input_args: Vec<OsString>) -> Result<()> {
     let ctx = session::KaniSession::new(args.common_opts)?;
 
     let outputs = ctx.cargo_build()?;
-    if ctx.args.only_codegen {
-        return Ok(());
-    }
+
     let mut goto_objs: Vec<PathBuf> = Vec::new();
     for symtab in &outputs.symtabs {
         goto_objs.push(ctx.symbol_table_to_gotoc(symtab)?);
     }
 
+    if ctx.args.only_codegen {
+        return Ok(());
+    }
+
     let linked_obj = outputs.outdir.join("cbmc-linked.out");
     ctx.link_goto_binary(&goto_objs, &linked_obj)?;
     if let Some(restrictions) = outputs.restrictions {
@@ -87,10 +89,12 @@ fn standalone_main() -> Result<()> {
     let ctx = session::KaniSession::new(args.common_opts)?;
 
     let outputs = ctx.compile_single_rust_file(&args.input)?;
+
+    let goto_obj = ctx.symbol_table_to_gotoc(&outputs.symtab)?;
+
     if ctx.args.only_codegen {
         return Ok(());
     }
-    let goto_obj = ctx.symbol_table_to_gotoc(&outputs.symtab)?;
 
     let linked_obj = util::alter_extension(&args.input, "out");
     {