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

[andrewrk]

Extracted from #14265.
Depends on #14183.

zig build should support fetching via an URL like this:

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

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.xz extension #14300

[scheibo]

should probably support .zst as well (or instead of .zstd) given thats the more common/standard extension for zstd

[andrewrk]

Typo, thank you

[dweiller]

I have a (mostly untested) branch that adds support for Zstandard compressed tarballs, but it first does some minor surgery on std.compress to make the high level decompession APIs more similar to try and use the current technique of making unpackTarball generic across formats. I've opened #14739 to get some input on how std.compress could be made more consistent across formats.