Fixes build error
```
error "It looks like you're trying to enable vendor availability
markup, but you haven't defined the corresponding macros yet!"
```
while trying to #include <__availability> header without having
the necessary preprocessor directive
`_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS` set
This commit fixes the build for LLVM 16 now that the toolchain has been
updated, and updates us to the latest available Zig commit.
The main patch changes are making more symbols available (and exposing
them through std.c.serenity) and working around new Zig build
requirements.
Co-Authored-By: Andre Herbst <moormaster@gmx.net>
:yakkie:
The build process for the Zig compiler is more involved than most of
the other ports, because the Zig compiler is mostly self-hosting. In
order to build it, the zig-bootstrap build system is used, which does
the following:
1) Build LLVM for the host OS;
2) Build Zig for the host OS with the SerenityOS target enabled;
3) Build zlib, zstd and LLVM for SerenityOS using `zig cc` as the C/C++
compiler;
4) Build Zig for SerenityOS using the host Zig.
A few hacks are required in order to tell `zig cc` and zig about what
Serenity's libc looks like in the build process, but other than that
it's fairly straightforward. All of the patches that are included with
this commit are Zig-upstream ready once the LLVM patches are upstreamed.
