If ragel 6.10 is not found, build it from source.
Seems to work, except that ragel uses exceptions and we configure
HarfBuzz build to not use exceptions, and I can’t find away to enable
exceptions only for the ragel subproject. I had to remove cpp_eh=none
from default options and try to disable exceptions in MSVC manually
(other compilers are already handled).
Khaled Hosny