builder: Support argument to the command with --run
builder: Support argument to the command with --run

For instance, this lets you do:

  flatpak-builder app foo.json ls -l

Without flatpak-builder complaining about not knowing "-l".

matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,amigadave/flatpak,GeorgesStavracas/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,handsome-feng/flatpak,amigadave/flatpak,handsome-feng/flatpak,amigadave/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,amigadave/flatpak