* GCC-7 and glibc-2.27 compat code
* Statically link libstdc++ for GCC based builds
Makes sure binaries which are built on a newer build host still work
on older distros.
* Use python3 when installing MacOS native tools
* Move actual build logic out of Travis and upgrade to gcc-7
Travis will now simply call a few scripts which do the actual work.
These scripts will first create a "builder image" which contains the
necessary environment for the actual build. Then scripts are called
inside this builder image to do the build.
This should make us more independant from Travis and also allows us
to do local CI testing.
The build matrix is also moved out of .travis.yml and instead moved
into ci/matrix.sh. This script is sourced with only "BUILD_TARGET" being
set so that it internally can figure out which other environment
variables need to be set.
This commit also upgrades the used GCC version to 7. This is due to the
use of ubuntu:bionic as base image for the builder image.
* Add Jenkinsfiles for regular CI and nightly gitian builds
* Automatically download OSX SDK in gitian-build.sh
* Remove bogus "export MAKEJOBS=-j5"
* Forward cache/src dirs into builder container
Fixes caching issues on Travis.
* fix
* Fail build immediately when building depends took too long
