Prefer writeManifestAndWatch unless you already added watch inputs
separately from using the cache system.
pub fn writeManifest(s: *Step, maker: *Maker, man: *Cache.Manifest) !void
pub fn writeManifest(s: *Step, maker: *Maker, man: *Cache.Manifest) !void {
if (s.test_results.isSuccess()) {
man.writeManifest() catch |err| switch (err) {
error.Canceled => |e| return e,
else => |e| try s.addError(maker, "failed writing cache manifest: {t}", .{e}),
};
}
}