I don't know if it was a change in gcc v9.2.0, but I had to add freetype2 to the #includes for ft2build.h:
find /usr/include/freetype2 -type f -name "*.h" \
-exec sed 's,<ft2build.h>,<freetype2/ft2build.h>,' -i {} \;
Error: ft2build.h not found.
