osx fixes for go 1.11

[kolyshkin]

This is a 3-in-1 story. Please have a seat.

Part 1.

Go 1.11 release notes say:

Go 1.11 now requires <...> macOS 10.10 Yosemite or later

So, change the OSX_VERSION_MIN in osxcross to 10.10.

Part 2.

MACOSX SDK tarball that was used before comes without libc++
headers, which are now required by at least crypto/x509 pkg
when compiling for Darwin. These include files are part of xcode,
which can only be downloaded by someone having Apple Developer ID,
which I don't have so this path is not available for me.

An alternative is to reuse the SDK tarball from the
https://github.com/multiarch/crossbuild project. Using it
fixes the following error:

# crypto/x509
osxcross: error: cannot find libc++ headers

Part 3.

The new tarball, although, misses the libtool package (apparently
somehow injected into the tarball that was used earlier) needed to
compile miekg/pkcs11 used by cli, which leads to errors like:

# github.com/docker/cli/vendor/github.com/miekg/pkcs11
vendor/github.com/miekg/pkcs11/pkcs11.go:28:10: fatal error: 'ltdl.h' file not found
#include <ltdl.h>
          ^
1 error generated.

To fix this one, libtool for osx need to be installed. Building it from
source (with osxcross) requires some other dependencies. Using brew is not
possible since it is Linux. Solution: download a binary package from brew
repo, cherry pick the needed stuff (lib and include).

Tested to fix docker-cli compilation issues on OSX using Go 1.11.

[vdemeester]

LGTM 🐸

[kolyshkin]

@vdemeester @thaJeztah PTAL

[thaJeztah]

These include files are part of xcode, which can only be downloaded by someone having Apple Developer ID, which I don't have so this path is not available for me.

@kolyshkin I do have a Mac developer subscription; would it be cleaner to update the package we have at dockerproject.org?

[kolyshkin]

I do have a Mac developer subscription; would it be cleaner to update the package we have at dockerproject.org?

I think we can reuse the one from this PR, it works fine and needs nothing.

It would be awesome though if you can upload it to s3.dockerproject.org. I tried to do it myself, logged in to aws successfully (using kir / docker-core credentials) but accessing S3 gives me "access denied".

[andrewhsu]

i'll put it up (working on getting the cache to play nice)

[andrewhsu]

$ curl -Is https://s3.dockerproject.org/darwin/v2/MacOSX10.10.sdk.tar.xz | head -1
HTTP/2 200

[kolyshkin]

Updated:

• move SDK tarball to dockerproject.org
• remove update to go 1.11.0
• add sha256 checksum validation for SDK tarball

[andrewhsu]

LGTM

[kolyshkin]

As per @thaJeztah suggestion I rolled back go version to 1.11.0.

The only problem with that is we already have a 1.11.0 tag in this repo. I am not sure how automatic docker image builds work... hope the tag can be just forcefully re-set to a new commit and it will trigger a rebuild. If not, we'll have to use a new tag, say something like 1.11.0-2, and use it, not a big deal either.

[thaJeztah]

LGTM