sync-all: END actions result in confusing error message

The instructions at Newcomers were slightly outdated, and result in a rather confusing error message:

$ ./sync-all --testsuite get
Unrecognised flag: --testsuite at ./sync-all line 872.
== Checking for old haddock repo
== Checking for old binary repo
== Checking for old mtl repo
== Checking for old Cabal repo
== Checking for old time from tarball
============================
ATTENTION!

You have an old time package in your GHC tree!

Please remove it (e.g. "rm -r libraries/time"), and then run
"./sync-all get" to get the new repository.
============================
== Checking for obsolete Git repo URL
$

The patch suppresses the misleading error message. I've already removed the --testsuite flag from the wiki page.

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	BuildingGhcFailed
Priority	normal
Resolution	Unresolved
Component	Build System
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