Always set something for RELEASE_NAME

- Move the setting of RELEASE_NAME outside of the check for whether or
not we're on Jenkins.
- Without having RELEASE_NAME set to something, Excelsior's fetching of
bootloader debs fails (and that's now required on external builds, as LK
source is not public).

Change-Id: I4d46e50f997525465895d258d83599f76fc43cff
diff --git a/preamble.mk b/preamble.mk
index be0925c..aa57cdb 100644
--- a/preamble.mk
+++ b/preamble.mk
@@ -17,10 +17,10 @@
 
 LOG := @$(ROOTDIR)/build/log.sh
 
+RELEASE_NAME ?= unstable
 ifneq ($(IS_JENKINS),)
   IS_EXTERNAL = true
   FETCH_PACKAGES = true
-  RELEASE_NAME ?= unstable
 endif
 
 ifeq (,$(wildcard /etc/dpkg/origins/glinux))