One can find it out with a decompiler and a lots and lots of free time. Compilers are not trivial programs, especially the ones needed to compile operating systems, with the required optimizations, and there are many ways to obfuscate code.

A better approach is to start with a small executable, one that translate hexadecimal numbers to binary, and from that build all the tools to compile a simple C compiler (such as the Tiny C Compiler, which is not very tiny), to compile the optimizing C compiler that can compile operating systems. That is the approach followed by the live-bootstrap project.