- Test runner will also check for leaks.

- `write` of qoi would leak memory.
- Issue when having an empty `Path` or just "."
- `set_env` would leak memory.

test/unit/stdlib/io/dstringstream.c3

@@ -4,10 +4,12 @@ fn void test_writing()
 {
 	DString foo;
 	foo.new_init();
+	defer foo.free();
 	OutStream s = &foo;
 	s.write("hello")!!;
 	s.write_byte('-')!!;
 	s.write("what?-------------------------------------------------------")!!;
+
 	ByteReader r;
 	String test_str = "2134";
 	io::copy_to(r.init(test_str), s)!!;