fix(build): prevent cargo cache invalidation from absolute OUT_DIR path

[cameronraysmith]

No description provided.

[cameronraysmith]

duckdb-rs/crates/libduckdb-sys/build.rs

Lines 185 to 187 in 538d7d8

	fn lib_name() -> &'static str {
	"duckdb"
	}

duckdb-rs/crates/libduckdb-sys/build.rs

Lines 140 to 144 in 538d7d8

	// Since the manifest controls the set of files, we require it to be changed to know whether
	// to rebuild the project
	println!("cargo:rerun-if-changed={out_dir}/{lib_name}/manifest.json");
	// Make sure to rebuild the project if tar file changed
	println!("cargo:rerun-if-changed=duckdb.tar.gz");

The absolute OUT_DIR path on L142 gets baked into cargo's fingerprint. When artifacts are reused across builds with different OUT_DIR values (nix, bazel, or simply cargo clippy vs cargo build in some configurations), cargo treats the path as missing and repeatedly rebuilds libduckdb-sys.

History:

• Rework bundled compilation to support included extensions #127 added rerun-if-changed={}/manifest.json (relative path) to track the file list
• rebuild on tar file change #163 added rerun-if-changed=duckdb.tar.gz which supersedes manifest.json tracking since manifest.json is extracted from the tarball
• fix: don't write files outside of OUT_DIR #347 moved extraction to OUT_DIR for sandbox compliance, changing manifest.json to an absolute path {out_dir}/{lib_name}/manifest.json

After #163, L142 became redundant. After #347, it also became non-portable. Deleting L142 fixes the portability issue with no change in rebuild semantics—L144 already covers it.