Add gcc to glance prereqs

Change-Id: I60584e5f3c99d15cd0f3a2222a448f7e01295779
diff --git a/files/apts/glance b/files/apts/glance
index 17c84ad..42d9fb8 100644
--- a/files/apts/glance
+++ b/files/apts/glance
@@ -1,3 +1,4 @@
+gcc
 python-eventlet
 python-routes
 python-greenlet