support fetching dependencies bundled with `.tar.xz` extension

[andrewrk]

Extracted from #14265.
Depends on #2851.

zig build should support fetching via an URL like this:

    .url = "https://example.com/foo.tar.xz",

zig/src/Package.zig

Lines 357 to 376 in 7cb2f92

	if (mem.endsWith(u8, uri.path, ".tar.gz")) {
	// I observed the gzip stream to read 1 byte at a time, so I am using a
	// buffered reader on the front of it.
	var br = std.io.bufferedReaderSize(std.crypto.tls.max_ciphertext_record_len, req.reader());
	var gzip_stream = try std.compress.gzip.gzipStream(gpa, br.reader());
	defer gzip_stream.deinit();
	try std.tar.pipeToFileSystem(tmp_directory.handle, gzip_stream.reader(), .{
	.strip_components = 1,
	});
	} else {
	return reportError(
	ini,
	comp_directory,
	uri.path.ptr,
	"unknown file extension for path '{s}'",
	.{uri.path},
	);
	}

Related:

• support fetching dependencies bundled with .tar.zst extension #14299

[nikkicoon]

with package manager hat on (pkgsrc), I have a question: will you consider people pre-fetching URLs out-of-band with an override for this and similar settings, since most system package managers do not have online enabled environments (for reproducibility and other reasons)? (in pkgsrc we wrap build-systems and repeated steps)

[nektro]

yes thats handled in #14281

[andrewrk]

pre-fetching URLs out-of-band

The system is designed to avoid network access when unnecessary. Combined with #14283, it would be trivial to ensure no network access by providing the directory pre-populated with the necessary dependencies.

And yes the mode hinted at in #14281 would likely make attempted network access by the build system into a compilation error.