upgrade to zig 0.12.1

src/run_tests.zig

@@ -182,7 +182,7 @@ pub fn main() !void {
     while (args.next()) |arg| {
         if (std.mem.eql(u8, "-h", arg) or std.mem.eql(u8, "--help", arg)) {
             try std.io.getStdErr().writer().print(usage, .{});
-            std.os.exit(0);
+            std.posix.exit(0);
         }
         if (std.mem.eql(u8, "--json", arg)) {
             out = .json;