Of note:
* The image now created by Dockerfile-base-mingw is available on wesnoth's Docker Hub.
* Strict building is disabled, as there are a couple warnings that show up when crosscompiling.
Use unbuffer to work around a travis issue when a secret is set in .travis.yml: https://github.com/travis-ci/travis-ci/issues/7967
As a bonus colored output of for example cmake now works again.
Also streamline test execution.
This adds running the WML schema validation in travis. It also updates the schema itself and fixes a few WML errors so that core and all campaigns under all difficulties pass the schema validation.
Travis now also makes use of this to set the optimization level for the -O0 builds, rather than extra_flags_*. This additionally fixes an issue where using -O0 in the release build with LTO resulted in the individual *.o files being compiled with -O0, but LTO then still linked with release's default -O3.
(cherry-picked from commit 63ff641662)
The intent behind this is that, if there most likely wouldn't be enough time left to complete the unit tests anyway, then just fail the job after compiling so the cache can be updated. Otherwise, if the unit tests were run and the job timed out, then the cache would not be uploaded at all and the next time the job ran it would be from scratch again.
(cherry-picked from commit 5d970e40cd)
Note: UBSan at least does seem to take a fairly significant amount of extra time to compile and run the WML tests with.
(cherry-picked from commit 92f74c39f6)
Adds the CXX_STD variable which can be set. Currently defaults to 14. This also now makes cmake honor the CXXSTD env variable set on travis.
(cherry-picked from commit 983045718a)
Currently will remain disabled everywhere, but this allows for enabling LTO for optimized, non-xcode jobs just by changing the value of the LTO variable.
Travis runs all commands in .travis.yml in its own wrapper script, so by sourcing steps/script.sh and then using exit explicitly, it resulted in the entire travis wrapper immediately terminating. With steps/script.sh no longer sourced, using exit works as expected again, and only exits steps/script.sh rather than quitting everything. Another solution, should sourcing steps/script.sh become necessary, is to use return instead of exit.
With that addressed, it's then possible to re-add printing the ccache statistics after the build ends while also making sure that the script exits with the return code of the xcodebuild/cmake+make command rather than the return code of the ccache statistics commands.
Travis looks at the return code of the final command run, and since printing the ccache statistics never fails, building would never be considered as failing. Manually calling exit also causes travis to treat the build as errored, since by sourcing the build it results in the entire travis wrapper shell exiting.
