This introduces a debug variant of the buildkit docker image. This
version builds the binary in a way that disables optimizations so that
it can be run properly with delve. It also builds and installs delve
only in the debug variant of the image.
For the debug variant, a shim `buildkitd` binary is created that execs
with the proper arguments to delve and forwards to the underlying
binary.
In order to use this version, you can set `--build-arg BUILD_VARIANT=debug`
and it will pick up this version of the image. The default is `release`.
The debug variant is only available for linux and the variant is ignored
for any other target os. Most other targets don't support `buildkitd` at
all so the only os this affects is freebsd.
delve is exposed on port 5000 by default and this can be accessed from
the host by using `-p 5000:5000`. If there is a port conflict on the
host, `-p XXXX:5000` can be used instead. It's also highly recommended
that you do `-p 127.0.0.1:5000:5000` instead. This is because docker
defaults to exposing ports to any interface which exposes the debug port
to the open internet. This is generally a good practice for running
buildkit on a tcp address anyway and the same applies to delve.
Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>
