Description: folly automatically picks up lz4 and unwind if they are found
by its cmake build script. This is causing buildbot failure.
Include these libraries in DEPENDS as well.

Test Plan:
 - build packages liblz4 and libunwind
 - build folly, and check that it throws an error
 - add this patch, and rebuild
 - verify that it succeeds this time around

Compile Tested: nbg6817, openwrt master

Maintainer: me
Signed-off-by: Amol Bhave <ambhave@fb.com>