Add build.zig to paths

Without this, the package manager will not include build.zig in the
fetched package, leading to the resulting package being unusable.

See ziglang/zig#18282

build.zig.zon

@@ -1,5 +1,5 @@
 .{
 	.name = "zig-cli",
 	.version = "0.8.0",
-	.paths = .{"./src", "./build.zig.zon"},
+	.paths = .{"./src", "./build.zig", "./build.zig.zon"},
 }