Add dir "srv" to the root file system

systemd-tmpfiles-setup.service tries to create a temporary
dir /srv but due to the read-only root file system it was
failing.

Resolves openbmc/openbmc#2231

Change-Id: I429b16a7736959583f24bf7fb4c6766cda24130a
Signed-off-by: Saqib Khan <khansa@us.ibm.com>
diff --git a/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend b/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend
index d7e7a3b..f282cde 100644
--- a/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend
+++ b/meta-phosphor/common/recipes-core/base-files/base-files_%.bbappend
@@ -3,3 +3,7 @@
 FILESEXTRAPATHS_prepend := "${@mf_enabled(d, 'obmc-ubi-fs', '${THISDIR}/${PN}:')}"
 
 RDEPENDS_${PN}_append += "${@mf_enabled(d, 'obmc-ubi-fs', 'mount-overlay-help')}"
+
+do_install_append() {
+    install -d ${D}/srv
+}