fetchgit: strip trailing whitespace

svn path=/nixpkgs/trunk/; revision=27862

pkgs/build-support/fetchgit/builder.sh

@@ -18,7 +18,7 @@ if test -n "$rev"; then
     parsed_rev=$(
         git rev-parse --verify "$rev" 2>/dev/null ||
         git rev-parse --verify origin/"$rev" 2>/dev/null
-    ) 
+    )
     git reset --hard $parsed_rev
     git checkout -b __nixos_build__
 else