Define apicheck function to use a Zig panic

[natecraddock]

From a quick glance at the Lua sources, it may be possible to override the use of assert.h for the API check with a custom function. If so, this would make api checks much more easy to debug with zig panics and stack traces.

And while we are here, should we make it possible to define LUA_USE_APICHECK manually (so it can be always on, or on in all safe modes?)

[robbielyman]

this is doable from consumer code:

pub fn main() void {
    // ...
    var act: std.posix.Sigaction = .{
        .handler = .{ .handler = handleAbrt },
        .mask = switch (builtin.os.tag) {
            .macos => 0,
            .linux => std.posix.empty_sigset,
            else => @compileError("os not supported"),
        },
        .flags = 0,
    };
    std.posix.sigaction(std.posix.SIG.ABRT, &act, null) catch {}; // if it doesn't work, we just crash the old way lol
    // ...
}

fn handleAbrt(_: c_int) callconv(.C) noreturn {
    @call(.always_inline, std.debug.panic, .{ "assertion failed!!", .{} });
}

[robbielyman]

here's a slightly better solution (zig 0.13, tested only on macOS so far):

pub fn main() void {
    // ...
    const act: if (builtin.mode == .Debug) std.posix.Sigaction = if (builtin.mode == .Debug) .{
        .handler = .{
            .handler = struct {
                fn handleAbrt(_: c_int) callconv(.C) noreturn {
                    std.debug.dumpCurrentStackTrace(@returnAddress());
                    std.process.exit(1);
                }
            }.handleAbrt,
         },
         .mask = if (builtin.os.tag == .linux) std.posix.empty_sigset else 0,
         .flags = 0,
     };
     if (builtin.mode == .Debug) try std.posix.sigaction(std.posix.SIG.ABRT, &act, null);
     // ...
}

this has the advantage that a stack trace is dumped in addition to the Lua library's assertion message. one disadvantage is that if other code (like for example std.debug.panicImpl) calls abort, you might see two stack traces. to guard against this, in seamstress v2 i put the stack trace dump inside a conditional which should only succeed if SIGABRT is raised by something other than std.debug.panicImpl