The idea here, is that if you can get a very basic C compiler, you can start building TinyCC, and eventually build a pre-C++ version of GCC, and from there build up to modern GCC. This is a lot easier said than done of course, but not quite as bad as needing the original compilers from the 70s!
https://bootstrappable.org/
https://www.gnu.org/software/mes/
The idea here, is that if you can get a very basic C compiler, you can start building TinyCC, and eventually build a pre-C++ version of GCC, and from there build up to modern GCC. This is a lot easier said than done of course, but not quite as bad as needing the original compilers from the 70s!