On linux, pass --as-needed to linker to avoid linking with unused shared libraries including libyaml.

debian/changelog

@@ -18,6 +18,8 @@ git-annex (5.20150618) UNRELEASED; urgency=medium
     running code and other things.
   * Support git's undocumented core.sharedRepository=2 value, which
     is equivilant to "world".
+  * On linux, pass --as-needed to linker to avoid linking with unused
+    shared libraries including libyaml.
 
  -- Joey Hess <id@joeyh.name>  Thu, 02 Jul 2015 12:31:14 -0400
 

git-annex.cabal

@@ -133,6 +133,11 @@ Executable git-annex
   -- Some things don't work with the non-threaded RTS.
   GHC-Options: -threaded
 
+  -- Avoid linking with unused dynamic libaries.
+  -- (Only tested on Linux).
+  if os(Linux)
+    GHC-Options: -optl-Wl,--as-needed
+
   if flag(network-uri)
     Build-Depends: network-uri (>= 2.6), network (>= 2.6)
   else