We should have the following USE flag to control vapi files as it is done with app-arch/gcab here https://bugs.gentoo.org/677454 18c18 < IUSE="gnome kde mono networkmanager perl python spidermonkey test webkit" --- > IUSE="gnome kde mono networkmanager perl python spidermonkey test vala webkit" 62,64c62 < # WITH_VALA just copies the .vapi file over and needs no deps, < # hence always enable it unconditionally < '-DWITH_VALA=ON' --- > "-DWITH_VALA=$(usex vala)"
Nothing has changed regarding the comment you are removing. Vala is not required for it, so we just let it copy it. USE=vala is not for controlling the copying of an already available *.vapi file, but about building the VAPI file from scratch and thus needing dev-lang/vala at runtime, or for other reasons (actually linking against vala, needing the compiler when the sources aren't pregenerated in tarball for an optional piece of code, etc)
According to https://packages.gentoo.org/useflags/vala the use flag controls the bindings which iiuc are the .vapi files. if USE=-vala is for the whole system why should we be copying this files along. Also upstream defaults to off: https://github.com/libproxy/libproxy/blob/master/INSTALL#L117
