meson: fix race condition in building

meson: fix race condition in building

the error
```
./src/modules/evas/engines/gl_generic/../software_generic/evas_ector_software.h:31:10: fatal error: 'evas_ector_software_buffer.eo.h' file not found
```
Came up when building efl on osx with meson. This is caused by the fact that gl_generic was build before the .eo files of evas_ector have been created in software_generic, this fixes this race condition by adding a new dependency to avoid that.

Reviewed-by: Stefan Schmidt <stefan@datenfreihafen.org>
Differential Revision: https://phab.enlightenment.org/D7831

Change-Id: I12e6413307c552c5b4fef7510cadc7678215874f