My Macbook reached 100 degrees Celsius while compiling a software package, is this normal?
Yes this is normal, Intel lists a "Thermal Junction" for the Intel® Core™ i7-3615QM Processor (6M Cache, up to 3.30 GHz) at 105 Degrees Celsius.  This CPU information is referenced from details in EveryMacs' Apple MacBook Pro "Core i7" 2.3 15" Mid-2012 Specs. Modern CPUs pretty much detect when there is a temperature problem and will shutdown if it detects that its overheating.

Large Compiling tasks can take the CPU to its limits, which is causing your MacBook Pro to have to dissipate way more heat that it does normally, hence why its hot and blaring its fans to keep it from overheating. This happens pretty much across the board with most Apple laptops when you push the CPU's to 100% for an extended period of time.

Ear plugs, a laptop stand, headphones, or a Mac Pro desktop (with whisper quiet fans) may be good accessories if you plan on compiling a lot of software packages on a regular basis.