[luatex] Lua interpreter difference between Windows and Mac

[Akira Kakuto]

> However, when I test the 
> same code on a Windows (10) machine,
> font_directory ends up being nil.

Probably kpse.find_file(filename) on windows without file type
searches TEXINPUTS by default. Try by adding file type as follows:

kpse.set_program_name('texlua')
font_target = "greciliae.ttf"
font_directory = kpse.find_file(font_target, 'truetype fonts')
print(font_directory)

Best,
Akira