[buildbot] phase1: add diffconfig step

[LEDE Commits]

jow pushed a commit to buildbot.git, branch master:
https://git.lede-project.org/1d1afc70dfce1e3bc2cd30fb0401be51f18dbde1

commit 1d1afc70dfce1e3bc2cd30fb0401be51f18dbde1
Author: Jo-Philipp Wich <jo at mein.io>
AuthorDate: Wed Jan 4 09:10:45 2017 +0100

    phase1: add diffconfig step
    
    Signed-off-by: Jo-Philipp Wich <jo at mein.io>
---
 phase1/master.cfg | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/phase1/master.cfg b/phase1/master.cfg
index 554fe4c..567dfec 100644
--- a/phase1/master.cfg
+++ b/phase1/master.cfg
@@ -531,6 +531,13 @@ for target in targets:
 	))
 
 	factory.addStep(ShellCommand(
+		name = "diffconfig",
+		description = "Generating config.seed",
+		command=["make", "-j1", "diffconfig", "V=s"],
+		haltOnFailure = True
+	))
+
+	factory.addStep(ShellCommand(
 		name = "checksums",
 		description = "Calculating checksums",
 		command=["make", "-j1", "checksum", "V=s"],