Inclusion of local headers should use quotes and not angle-brackets.
The incorrect usage is presumably a leftover from the brushlib days.

Bashscript doing the replacements w. sed, for reference:

for h in ls *.h */*.h; do
    sed -i -E "s|^#include\s*<$h>|#include \"$h\"|g"\
        ./*.{h,c} ./*/*.{h,c}
done