build: lib: harmonize the use of package_c_args in all libs

build: lib: harmonize the use of package_c_args in all libs

Add it to subprojects which are not using it and remove and old
ELEMENTARY_BUILD define we no longer use. This allows us to have a
central place in the main meson.build file to set this variable.

Reviewed-by: Marcel Hollerbach <mail@marcel-hollerbach.de>
Reviewed-by: Vincent Torri <vincent.torri@gmail.com>
Reviewed-by: João Paulo Taylor Ienczak Zanette <joao.tiz@expertisesolutions.com.br>
Differential Revision: https://phab.enlightenment.org/D11854