add APT_GET_OPTIONS to let jobs specific command line flags

This is for things like adding --allow-unauthenticated when using CI aptly
repos.

gitlab-ci-git-buildpackage

@@ -11,23 +11,28 @@ if [[ ! -f $lockfile ]] ; then
     set -e
     set -x
 
+    apt_get="apt-get -qy"
+    if [ ! -z "$APT_GET_OPTIONS" ]; then
+        apt_get="$apt_get $APT_GET_OPTIONS"
+    fi
+
     if [ ! -z "$DEBIAN_RELEASE" ]; then
         sed -i "s, testing , $DEBIAN_RELEASE ," /etc/apt/sources.list
     fi
 
-    apt-get -qy update
-    apt-get -qy dist-upgrade
+    $apt_get update
+    $apt_get dist-upgrade
 
     cd $CI_PROJECT_DIR
     if dpkg --compare-versions `dpkg -s apt |sed -n 's,^Version: \(.*\),\1,p'` ge 1.1; then
-        apt-get -qy build-dep $CI_PROJECT_DIR
+        $apt_get build-dep $CI_PROJECT_DIR
     else
         # this is running on an older version, like jessie-backports
         export BUILD_DEPENDS=`sed 's/\s*|[^,]*,/,/g' debian/control | perl -ne 'next if /^#/; $p=(s/^Build-Depends:\s*/ / or (/^ / and $p)); s/,|\n|\([^)]+\)//mg; print if $p'`
-        apt-get -qy install --no-install-recommends \
+        $apt_get install --no-install-recommends \
                 build-essential fakeroot git-buildpackage pristine-tar $BUILD_DEPENDS
     fi
-    apt-get -qy autoremove --purge
+    $apt_get autoremove --purge
     dpkg-checkbuilddeps
     echo "ensure pristine-tar branch exists and is current"
     git clean -fdx