Move build system to zig build

[rdunnington]

Closes #25. This change ports the python-based orcadev build system to build.zig. Some immediate benefits:

• Caching of intermediate artifacts - speeds up the build time for iterative builds.
• Dependency tracking - don't have to worry about remembering to build specific dependencies for a given library.
• Wasm support - no need to manually install the wasm compiler_rt builtins
• Single compiler used for all builds - drops MSVC on windows
• Avoids annoying issues with brew vs apple versions of clang on macos
• --watch flag that watches for changes to any input files and rebuilds dependent artifacts

There are a few guiding design principles for this change:

• Try to preserve the original behavior of orcadev and the locations of build artifact outputs as much as possible.
• zig build XXX should just work on any system, regardless of system-installed dependencies. For example, if we require python to be present for part of the build, the build system should ensure a compatible version to be installed so the user doesn't have to, such as via build.zig.zon.
• Zig should be used to implement everything used in the build system, including helper programs, to avoid too much language-hopping.

Note that this is a draft and there still remains a bunch of work to be done before this can go in. Namely:

• Switch zig build to run zig build orca-install by default
• Don't require presence of orca executable in PATH if --sdk-dir is supplied to zig build orca-install
• Investigate angle prebuilt artifact false mismatch
• Investigate sample startup perf differences between old builds and zig build system
• Try to repro Skytrias' missing openssl issue and ensure zig build handles that case
• Update CI scripts orcabuild -> zig build
• Add test job to CI with zig build test
• Add sketches to CI
• Update README
• Try to get delay-loading to work for graphics DLLs on windows (webgpu, EGL, GLESv2)
• Port macos @rpath stuff from dev.py
• Address remaining TODOs
• Cleanup dead or other commented-out code
• Collapse commit history

[bvisness]

I ran into an issue with the latest Zig from Homebrew (which is the latest Zig release afaik):

% zig build
/Users/bvisness/Developer/orca-app/orca/build.zig:292:34: error: no field or member function named 'addUpdateSourceFiles' in 'Build'
    var stage_angle_artifacts = b.addUpdateSourceFiles();
                                ~^~~~~~~~~~~~~~~~~~~~~
/opt/homebrew/Cellar/zig/0.13.0_1/lib/zig/std/Build.zig:1:1: note: struct declared here
const std = @import("std.zig");
^~~~~
referenced by:
    runBuild__anon_8422: /opt/homebrew/Cellar/zig/0.13.0_1/lib/zig/std/Build.zig:2117:37
    main: /opt/homebrew/Cellar/zig/0.13.0_1/lib/zig/compiler/build_runner.zig:301:29
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

[rdunnington]

Yeah as mentioned in discord you need one of the 0.14 dev releases from master to build this - there were a few patches needed to get this working.