deps.sh: Run apt-get update

Hopefully this will fix the CI tests. This is a common enough issue on
CI that Travis mentions it in their documentation:
https://docs.travis-ci.com/user/common-build-problems/#linux-apt-fails-to-install-package-with-404-error

scripts/deps.sh

@@ -13,6 +13,7 @@ source /etc/os-release
 
 msg "Installing system build dependencies"
 if [[ "${ID}" =~ "debian" ]] || [[ "${ID_LIKE}" =~ "debian" ]]; then
+    sudo apt-get update
     sudo apt-get install \
         --no-install-recommends \
         --yes \