ci: bring back build tests (#1813)

This directory was deleted when `cargo hack` was introduced, however
there were some tests that were still useful (macro failure output).

Also, additional build tests will be added over time.

tests-build/tests/fail/macros_invalid_input.rs

@@ -0,0 +1,25 @@
+use tests_build::tokio;
+
+#[tokio::main]
+fn main_is_not_async() {}
+
+#[tokio::main(foo)]
+async fn main_attr_has_unknown_args() {}
+
+#[tokio::main(threadpool::bar)]
+async fn main_attr_has_path_args() {}
+
+#[tokio::test]
+fn test_is_not_async() {}
+
+#[tokio::test]
+async fn test_fn_has_args(_x: u8) {}
+
+#[tokio::test(foo)]
+async fn test_attr_has_args() {}
+
+#[tokio::test]
+#[test]
+async fn test_has_second_test_attr() {}
+
+fn main() {}