Use the same Makefile build system as Gen 1+2 repos for macOS compatibility

[Rangi42]

macOS comes with BSD GNU 3.81 make, which is more limited than modern make. The system that pokegold-spaceworld uses for putting object files in a build/ directory breaks the build on macOS:

% make compare
make: *** No rule to make target `build/home/audio.o', needed by `pokegold-spaceworld.gb'.  Stop.

Users have to install GNU make from Homebrew or MacPorts:

% gmake compare
mkdir -p build/home/
mkdir -p build/engine/battle/
...
rgbasm -o rgbdscheck.o rgbdscheck.asm
rgbasm -E -i build/ -DGOLD -o build/home/audio.o home/audio.asm
rgbasm -E -i build/ -DGOLD -o build/home/bankswitch.o home/bankswitch.asm
...
pokegold-spaceworld.gb: OK
pokegold-spaceworld-correctheader.gb: OK

[Narishma-gb]

Something else to note when refactoring Makefile:

make clean does not remove rgbdscheck.o

On Unix, direct execution of python scripts could fail due to permissions errors, perhaps add $(PYTHON) ?

[Rangi42]

make tidy and make clean do remove rgbdscheck.o in pokered and pokecrystal, and it would defeat the purpose of rgbdscheck if an outdated .o file sticks around, so it should also be removed here.

[Rangi42]

Python is no longer needed for any build tasks, so PYTHON := python3 should be deleted from the Makefile. (The tools written in C run faster and avoid any compatibility issues with the user's Python version.)

[Narishma-gb]

make tidy and make clean do remove rgbdscheck.o in pokered and pokecrystal, and it would defeat the purpose of rgbdscheck if an outdated .o file sticks around, so it should also be removed here.

I completely agree, I should have added "as it should do".
As for python, I think this build still relies on it to generate build/shim.asm. It's needed to link the undumped ROM symbols to a bank and address.

[Rangi42]

Oh, you're right, MAKE_SHIM := tools/make_shim.py. Probably not worth rewriting that in C, it's a temporary tool. $(PYTHON) tools/make_shim.py $< > $@ would be fine.

[mid-kid]

macOS comes with BSD make

Maybe a bit pedantic but it's not BSD make, it's GNU make 3.81 (the last GPLv2 version), which lacks some more modern features and has some bugs that need to be kept in mind. If this project had to support BSD make, it'd be tied to a very limited set of common functionality.

The existing makefile can be made to work with 3.81, but I forget which specific bug causes this - I've had to fix similar things before.