Buck checkstyle fix for Jenkins

Change-Id: I6009bb1ef8a9394375c0a298f91ef46c86c05606
diff --git a/bucklets/onos.bucklet b/bucklets/onos.bucklet
index 0a530e7..24d887f 100644
--- a/bucklets/onos.bucklet
+++ b/bucklets/onos.bucklet
@@ -110,7 +110,7 @@
 
   ### Checkstyle
   if srcs:
-    chk_cmd = '#!/bin/sh\n'
+    chk_cmd = '#!/bin/bash\n'
     # FIXME hack to add dependency on suppressions-xml in the checkstyle rule
     chk_cmd += 'FOO="$(location //tools/build/conf:suppressions-xml)"\n'
     base = get_base_path()