meta-google: Add bbapend for rng-tools

Set jitter to use only single thread. gBMC systems will always at least
2 CPU, so it won't take up everything.

Change-Id: I43215a4ebca680d3d340062cc9f99a33ab36a60f
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/meta-google/recipes-support/rng-tools/rng-tools/default b/meta-google/recipes-support/rng-tools/rng-tools/default
new file mode 100644
index 0000000..8309246
--- /dev/null
+++ b/meta-google/recipes-support/rng-tools/rng-tools/default
@@ -0,0 +1 @@
+EXTRA_ARGS="-r /dev/hwrng -O jitter:thread_count:1"
diff --git a/meta-google/recipes-support/rng-tools/rng-tools_%.bbappend b/meta-google/recipes-support/rng-tools/rng-tools_%.bbappend
new file mode 100644
index 0000000..cf51f85
--- /dev/null
+++ b/meta-google/recipes-support/rng-tools/rng-tools_%.bbappend
@@ -0,0 +1,3 @@
+FILESEXTRAPATHS:prepend:gbmc := "${THISDIR}/${PN}:"
+
+SRC_URI:append:gbmc = " file://default"