build: Install httpcache if installed-tests are enabled
build: Install httpcache if installed-tests are enabled

Signed-off-by: Simon McVittie <smcv@debian.org>

Closes: #1989
Approved by: alexlarsson

flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak