backport c4b5b002c3
make swss build depends only on libsairedis instead of syncd. This allows to build swss without depending
on vendor sai library.
Currently, libsairedis build also buils syncd which requires vendor SAI lib. This makes difficult to build
swss docker in buster while still keeping syncd docker in stretch, as swss requires libsairedis which also
build syncd and requires vendor to provide SAI for buster. As swss docker does not really contain syncd
binary, so it is not necessary to build syncd for swss docker.
[submodule]: update sonic-sairedis
* 9a66890 2020-06-28 | [build]: add option to build without syncd (HEAD -> 201811, origin/201811) [Guohan Lu]
Signed-off-by: Guohan Lu <lguohan@gmail.com>
