Merge pull request #261 from akgrant43/travis_update

Run "apt-get update" on debian platforms to ensure the package cache is up to date, and avoid errors similar to:

E: Failed to fetch http://package.deb 404 Not Found [IP: a.b.c.d]

This issue was documented on the Travis CI status page (https://www.traviscistatus.com/incidents/fvch7h32ncf1) on May 9:

"We have changed the build script to not default to running apt-get update for the time being, unless we're able to auto-detect that your build uses apt-get install. If your build requires it in other ways, please do opt in via .travis.yml. The build log gives instructions on how to opt in."

.travis.yml

@@ -2,6 +2,10 @@ language: c
 
 sudo: required
 
+addons:
+    apt:
+      update: true
+
 cache:
   directories:
   - armchroot

.travis_install.sh

@@ -1,6 +1,7 @@
 set -e
 
 if [[ "${ARCH}" = "linux64x64" ]]; then
+    sudo apt-get update -y
     sudo apt-get install -yq --no-install-suggests --no-install-recommends --force-yes \
             debhelper \
             devscripts \
@@ -16,6 +17,7 @@ if [[ "${ARCH}" = "linux64x64" ]]; then
             gcc-multilib \
             uuid-dev
 elif [[ "${ARCH}" = "linux32x86" ]]; then
+    sudo apt-get update -y
     sudo apt-get remove -q -y gvfs-daemons
     sudo apt-get install -yq --no-install-suggests --no-install-recommends --force-yes \
             devscripts \
@@ -59,6 +61,7 @@ sudo apt-add-repository multiverse
 sudo apt-add-repository universe
 sudo apt-get update -myq || true
 
+sudo apt-get update -y
 sudo apt-get install -yq --no-install-suggests --no-install-recommends --force-yes \
      gcc-arm-linux-gnueabi \
      gcc-arm-linux-gnueabihf \