idk if you still have this issue but how it have it set up is:
libraylib.a is lib/
raylib.h in include/
and i have the main.c file in the source/ folder
and from the build/ bolder i run this
gcc -static -static-libgcc -static-libstdc++ ../source/** -o game.exe -O2 -Wall -Wno-missing-braces -I ../include/ -L ../lib/ -lraylib -lopengl32 -lgdi32 -lwinmm -mwindows
(the same thing works on c++ just replace gcc with g++)