It all happened when I decided to run Geekbench 5 on my phone: surprisingly the single-core performance matched my 'old'¹ Pentium T3200 and surpassed it in multicore. Since I've been having fun with distcc for the last few days, I asked myself: 'Can my phone really help my old laptop build faster? nah, hard to believe... but let's try'.
Without further ado: YES. Not only can my phone be faster, but it can significantly help in the build process, I believe the results below speak for themselves:
Building Git (#30cc8d0) on a Pentium T3200, 8m30s
Building Git (#30cc8d0) on a Pentium T3200 (2x 2.0 GHz)+ Snapdragon 636 (4x1.8 + 4x1.6 GHz), 2m9s