The method described in the page you reference, does not exclude the possibility that the compiler you start with, contains malicious code, and recognizes that it is compiling the GCC code base. It is not true bootstrapping as described in [0]. If you read through [1] you will see that even getting a fairly recent version of TCC to compile is not that simple.
At that level of a paranoia, there's no guarantee that the CPU doesn't contain a malicious method for detecting and modifying compiler builds, so you better build your own CPU out of TTL chips ;)
[0] https://bootstrappable.org/ [1] https://bootstrapping.miraheze.org/wiki/Live-bootstrap