Add a way to specify a custom graphdriver priority list
during build. This can be done with something like
go build -ldflags "-X github.com/docker/docker/daemon/graphdriver.priority=overlay2,devicemapper"
As ldflags are already used by the engine build process, and it seems
that only one (last) `-ldflags` argument is taken into account by go,
an envoronment variable `DOCKER_LDFLAGS` is introduced in order to
be able to append some text to `-ldflags`. With this in place,
using the feature becomes
make DOCKER_LDFLAGS="-X github.com/docker/docker/daemon/graphdriver.priority=overlay2,devicemapper" dynbinary
The idea behind this is, the priority list might be different
for different distros, so vendors are now able to change it
without patching the source code.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Upstream-commit: 17708e72a7ef29fb1d4b03fbded1c5e4c08105fd
Component: engine
0db60dff81