After reading this blog post by Jason Dagit with the same title as the one you are reading now, I opened a new terminal session and cloned the GHC repo to my computer. Then, I successfully built GHC. Easy and faster than I thought. Online docs talk about hours of compiling process, when for me it only took some minutes (about 20-30 minutes). But, yeah, I provided the -j3 parameter to compile it in parallel. It works like a charm.
After having GHC built from the source for my first time, I decided to make a modified version of GHC. This version is aimed to really professional Haskell hackers who don't need any help from any source to know which commands are available in GHCi.
This is just my first step to get involved in GHC coding. :)