Root cause of the broken 'Sign in with Plex' and update links on
portable builds: the bundle ships Ubuntu's libgio, whose compiled-in
helper path (/usr/lib/x86_64-linux-gnu/glib-2.0/gio-launch-desktop)
exists only on Debian-family hosts. glib then falls back to a bare PATH
search, and distros like Fedora keep the helper in /usr/libexec outside
PATH, so every URL/desktop-file spawn failed. Installing the RPM masked
it only because system glib is built with the right path.
Bundle the build host's gio-launch-desktop next to the libgio it was
built with (bundle-libs.sh now fails the build if libgio is bundled and
the helper cannot be found) and export GIO_LAUNCH_DESKTOP from plezy.sh,
which glib checks before its compiled-in path. Covers the tarball and
the deb/rpm/pacman packages alike, since they all ship the same bundle
and launch through the wrapper.
close#1477
edde746