wget: restore build-time dep on XZ for HEAD
dub: remove custom download strategy
salt: remove custom download strategy
l-smash: set GIT_DIR instead of symlinking
libcouchbase: set GIT_DIR instead of symlinking
syncthing: set GIT_DIR instead of symlinking
pulse: set GIT_DIR instead of symlinking
syncthing 0.10.12

Version bump.

Closes #35041.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
syncthing: update 0.10.12 bottle.
Update capnp to 0.5.0