In 2013 I also worked as first time contributor on a bug that affected the linux version of Firefox.
Firefox took 2 hours to compile in my pentium dual-core Intel laptop, it was in August so warm inside the house, the 2 hours compiling at closer 100% cpu made the laptop halt due to excessive temperature before finishing. I also recall the build failed because of out-of-memory error (ram exhausted) I had 2GB and had to expand to 4 GB or something like that.
After overcoming the struggles I was finally happy as the fix was committed.
I had a similar experience when building Firefox from source >.<
though I recall I had more trouble when pulling the codes as I was naive and pulled all the history