Support symlinking git-annex and git-annex-shell from the Linux standalone bundle into PATH.

Unless busybox doesn't support readlink -f, then it just uses readlink and
symlinking won't work. Also, OSX has no readlink -f so not done there.

Thanks, jlebar.

standalone/linux/skel/git

@@ -1,5 +1,5 @@
 #!/bin/sh
-link="$(readlink "$0")" || true
+link="$(readlink -f "$0" 2>/dev/null || readlink "$0")" || true
 if [ -n "$link" ]; then
 	base="$(dirname "$link")"
 else