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>

folly is an open-source C++ library developed and used at Facebook.
Adding this package will enable adding further packages that depend on
this.

Depends on PR #7098, PR #7101, PR #7126, PR #7877

Maintainer: me
Compile tested: openwrt-18.06 for ipq40xx, ipq806x, x86 and ar71xx
Run tested: Tested on devices running on the above architectures.
Verified that dependent packages can successfully build and run using
the libfolly.so shared library.

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