mongoose.c is ridiculously big or gcc requires unreasonably large RAM to build mongoose.c

I just built on a RPI3 running 32-bit Raspberry Pi OS. Building mongoose.c took over 6 minutes. That's ok. But it consumed the entire memory and pushed the machine into paging. I really don't know what the fix is here, but it's a bug if rtl_433 can't be built on a machine with 1GB of RAM. That's a violation of the implied specification of merchantablity and fitness for use. (Yes, I know I could set up cross builds.)