Add All_syzygy target to GN build.

TBR=brettw@chromium.org, sebmarchand@chromium.org, brucedawson@chromium.org
BUG=525752

Review-Url: https://codereview.chromium.org/2094103002
Cr-Commit-Position: refs/heads/master@{#402081}
1 file changed