dbus: Add a Linux post-link for CI systems

Travis-CI does not have an `/etc/machine-id` file which dbus
would otherwise use as a UUID. However, before checking that
file it looks for `${PREFIX}/var/lib/dbus/machine-id`.

When necessary we create `${PREFIX}/var/lib/dbus/machine-id`
from `/proc/sys/kernel/random/boot_id` or else `/dev/random`

dbus/meta.yaml

@@ -7,7 +7,8 @@ source:
   sha1: e1d3dedd1d2b7305464d6892579fee3ad9639355
 
 build:
-  number: 1
+  number: 3
+  detect_binary_files_with_prefix: true
 
 requirements:
   build:

dbus/post-link.sh.Linux

@@ -0,0 +1,14 @@
+if [ ! -f /etc/machine-id ]; then
+    echo "dbus post-link :: /etc/machine-id not found .." >> ${PREFIX}/.messages.txt
+    if [ ! -d ${PREFIX}/var/lib/dbus ]; then
+        mkdir -p ${PREFIX}/var/lib/dbus
+    fi
+    if [ -f /proc/sys/kernel/random/boot_id ]; then
+        echo "dbus post-link :: .. using /proc/sys/kernel/random/boot_id" >> ${PREFIX}/.messages.txt
+        cat /proc/sys/kernel/random/boot_id | tr -d '-' > ${PREFIX}/var/lib/dbus/machine-id
+    else
+        echo "dbus post-link :: .. /proc/sys/kernel/random/boot_id not found either .." >> ${PREFIX}/.messages.txt
+        echo "dbus post-link :: .. using /dev/random" >> ${PREFIX}/.messages.txt
+        od -N16 -An -tx1 < /dev/random | tr -d '[:space:]' > ${PREFIX}/var/lib/dbus/machine-id
+    fi
+fi