package/leveldb: fix detection of the snappy library

Pull a patch pending in an upstream pull request to fix the detection
of the snappy library when we are in static linking configurations.

Fixes:

  https://bugs.busybox.net/show_bug.cgi?id=12671



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>