fix: don't write files outside of OUT_DIR

[frectonz]

The cargo docs state that build.rs scripts should not write files outside of the OUT_DIR.

In general, build scripts should not modify any files outside of OUT_DIR. It may seem fine on the first blush, but it does cause problems when you use such crate as a dependency, because there’s an implicit invariant that sources in .cargo/registry should be immutable. cargo won’t allow such scripts when packaging.

Taken from here.

Some build environments like Nix use this information to provide a sandbox environment for build.rs scripts to run. These sandbox environments fail the build if the script tries to modify files that are not in the OUT_DIR.

The modification being done in this crate is the extraction of the DuckDB source archive. Currently, the archive is being extracted in the root directory of the libduckdb-sys crate. This causes the build to fail in sandbox environments.

In this PR, I have modified the build.rs script for libduckdb-sys to extract the DuckDB archive in the OUT_DIR. I have also added some code to delete all the extracted source files from the OUT_DIR after the compilation is completed because they will no longer needed.

[frectonz]

The clippy warnings in the failed CI run are not part of my changes.

[Mytherin]

Thanks!