gnu: Use invoke and return #t from all builders.
* gnu/packages/admin.scm, gnu/packages/android.scm, gnu/packages/audio.scm,
gnu/packages/avr.scm, gnu/packages/base.scm, gnu/packages/bioinformatics.scm,
gnu/packages/certs.scm, gnu/packages/check.scm, gnu/packages/code.scm,
gnu/packages/commencement.scm, gnu/packages/dictionaries.scm,
gnu/packages/docbook.scm, gnu/packages/emacs.scm, gnu/packages/embedded.scm,
gnu/packages/fonts.scm, gnu/packages/games.scm, gnu/packages/gnome.scm,
gnu/packages/gnu-doc.scm, gnu/packages/guile.scm, gnu/packages/hurd.scm,
gnu/packages/javascript.scm, gnu/packages/libreoffice.scm,
gnu/packages/linux.scm, gnu/packages/lisp.scm, gnu/packages/lxde.scm,
gnu/packages/mail.scm, gnu/packages/markup.scm, gnu/packages/mate.scm,
gnu/packages/pkg-config.scm, gnu/packages/qt.scm, gnu/packages/rust.scm,
gnu/packages/scheme.scm, gnu/packages/sdl.scm, gnu/packages/statistics.scm,
gnu/packages/syncthing.scm, gnu/packages/tex.scm, gnu/packages/web.scm,
gnu/packages/wine.scm, gnu/packages/xfce.scm: In the builders of packages
using 'trivial-build-system', use invoke where appropriate, raise exceptions
on errors, and otherwise return #t.
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