* no longer depend on apt.llvm.org, instead we rely on a zig-bootstrap
tarball with pre-built Zig, LLVM, LLD, and Clang. Similar to the
Windows Dev Kit but for Linux. This also makes the script no longer
depend on Docker, libxml2, or GCC.
* remove bash retry logic; it was only needed for flaky apt.llvm.org
and isn't needed for the other resources we download.
* build and upload the experimental std lib automatically generated
docs. langref.html is moved to docs/langref.html because the std lib
docs are in docs/std/.
* the superfluous "zig" directory in $prefix/lib/zig/std/std.zig is
removed from the tarball.
* update_download_page makes a commit in the www.ziglang.org repository
updating data/releases.json so that repository can manage deploys.
ce5222d945