Start building sysrepo-ietf-alarms

The project also requires date library[1] but it was not running
correctly on our ARM. I had to patch the library with the workaround
from [2], hence the buildroot update.

[1] https://github.com/HowardHinnant/date
[2] https://github.com/HowardHinnant/date/issues/252

Change-Id: Ie82b8c9ea50b0198b024256ff81d67ba7344c190
diff --git a/.gitmodules b/.gitmodules
index 7a7d552..744946f 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -19,3 +19,6 @@
 [submodule "submodules/rousette"]
 	path = submodules/rousette
 	url = ../rousette
+[submodule "submodules/sysrepo-ietf-alarms"]
+	path = submodules/sysrepo-ietf-alarms
+	url = ../sysrepo-ietf-alarms