do not install recovery on boot
fix up adb to prefer /sbin/sh if it exists

Change-Id: Ifa68efec387e6c12dc4bb2d0e764b8ecf96c0ad5
sdcard: Allow building as a static library

 * Split main() out in order to allow linking with a multi-call
   executable such as recovery.

Conflicts:
	sdcard/Android.mk

Change-Id: I3325135e47e4dd5af3912f5ce67ec64007d54a63