I thought I'd post a diff of the "test_asset_builder.*" files which have
support for xlib core text and the stb_truetype library, in case it is
helpful to anyone.

The kanji characters show up as the default glyph (plain rectangle) in both
implementations, which makes sense for core xlib, as I don't think the
xserver based fonts have the kanji glyphs, even if the required locale
changing was implemented.

But I don't know why stb_truetype returns the default glyph for the kanji characters, because they exist in the *.ttf files.