Allow to install os-resource-classes from git repo

Example local.conf config snippet:

LIBS_FROM_GIT="os-resource-classes"
OS_RESOURCE_CLASSES_REPO="${LOCAL_GIT_BASE}/os-resource-classes"
OS_RESOURCE_CLASSES_BRANCH="dev_branch"

Closes-Bug: #1934784
Change-Id: I972a2a49aa816433152e5cfac4f672c0465d083f
diff --git a/stackrc b/stackrc
old mode 100644
new mode 100755
index 0501659..620b1fc
--- a/stackrc
+++ b/stackrc
@@ -548,6 +548,10 @@
 GITBRANCH["neutron-lib"]=${NEUTRON_LIB_BRANCH:-$TARGET_BRANCH}
 GITDIR["neutron-lib"]=$DEST/neutron-lib
 
+# os-resource-classes library containing a list of standardized resource classes for OpenStack
+GITREPO["os-resource-classes"]=${OS_RESOURCE_CLASSES_REPO=:-${GIT_BASE}/openstack/os-resource-classes.git}
+GITBRANCH["os-resource-classes"]=${OS_RESOURCE_CLASSES_BRANCH:-$TARGET_BRANCH}
+
 # os-traits library for resource provider traits in the placement service
 GITREPO["os-traits"]=${OS_TRAITS_REPO:-${GIT_BASE}/openstack/os-traits.git}
 GITBRANCH["os-traits"]=${OS_TRAITS_BRANCH:-$TARGET_BRANCH}