The extension is completely arbitrary since ebml_defs.c isn't a real c
file that actually is compiled at any point in time. It's just used as
an include. The reason for changing the extension is because meson needs
to add this to its list of sources for dependency/ordering purposes.
Understandably, meson will try to compile any .c file added to a c
project executable object. Obviously, this compilation will never
succeed, and this shouldn't be compiled anyways. Just make it .inc
instead.