This commit updates the version of manylinux base images to use custom
flavor having Python 3.8. See https://github.com/scikit-build/manylinux#available-branches
Python 3.8.0a2 was initially added to upstream manylinux
after integrating https://github.com/pypa/manylinux/pull/273.
But considering that Python 3.8 is still an alpha release and that
(1) the associated ABI is not yet stable and (2) incompatibilities are
expected between wheels generated for alpha/beta/rc and final version
of python 3.8.0, the manylinux maintainers decided to revert the update.
Older versions of git included in older linux distributions are not able
to download source from Github. A newer version is required with a newer
OpenSSL. This requires to also build curl with the same OpenSSL.
CMake is downloaded precompiled if available (64bits system) or compiled
from source otherwise.
This commit build each images with the following arguments:
* IMAGE: Name of the image (e.g dockcross/base, dockcross/manylinux-x64, ...)
* VCS_REF: dockcross/dockcross commit from which this image is built
* VCS_URL: this repository obtained reading remote.origin.url
* BUILD_DATE: Date and time when the build was initiated
Then, within the Dockerfile, the metadata are associated with the image
using the "LABEL" instruction.
See https://docs.docker.com/engine/reference/builder/#/label
The corresponding labels can be found here:
http://label-schema.org/rc1/#build-time-labels
See #28
