You're right, I should've included that from the get-go. Included one now, hope it helps :)
For reference, I got it running on my Linux system with the following changes:
Change LDFLAGS: LDFLAGS=`pkg-config sdl2 --libs --cflags` -g -lm
In interrupt.c, change the two #import lines to #include.
Here is some inspiration: https://github.com/dolphin-emu/dolphin