Allow BusyBox to be invoked as "<something>-busybox". This is
necessary when it's run from the Nix store as <hash>-busybox during
stdenv bootstrap.

diff -ru -x '*~' busybox-1.22.1-orig/libbb/appletlib.c busybox-1.22.1/libbb/appletlib.c
--- busybox-1.22.1-orig/libbb/appletlib.c	2014-01-09 19:15:44.000000000 +0100
+++ busybox-1.22.1/libbb/appletlib.c	2014-10-29 09:53:01.232052068 +0100
@@ -764,7 +764,7 @@
 	int applet = find_applet_by_name(name);
 	if (applet >= 0)
 		run_applet_no_and_exit(applet, argv);
-	if (strncmp(name, "busybox", 7) == 0)
+	if (strstr(name, "busybox") != 0)
 		exit(busybox_main(argv));
 }