[Bug modula2/116123] flex generated files should be committed to the tree so that flex is not needed on build

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116123

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
flex is required for building GCC from git even without m2.

gengtype-lex.l needs to be processed by flex.