chore: Fix build failures

[IndrajeetPatil]

@krlmlr This is still going to fail because the tests don't run successfully.

It's because the tests can't find the local path "/Users/kirill/git/R/duckdb/tools/rpkg/src/duckdb.so":

── Test failures ──────────────────────────── testthat ────

> library("testthat")
> 
> test_check("adbc")
Loading required package: adbc
Error in normalizePath(path, mustWork = TRUE) : 
  path[1]="/Users/kirill/git/R/duckdb/tools/rpkg/src/duckdb.so": No such file or directory
Calls: test_check ... <Anonymous> -> adbc -> load_driver -> normalizePath
Execution halted

[IndrajeetPatil]

I also don't seeduckdb.so file here.

[krlmlr]

We need to fix a few things upstream for this to work. Please ignore for now.