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 63ff641662d4192401a49f9a002d7872000a3f02)
This allows having multiple Dockerfile-base-* files without also needing to add a separate Dockerfile-travis-* file due to the FROM line changing.
(cherry-picked from commit 3f67c2fbf051aa9e322defb66c782477cd53b8bd)
This makes it simpler in the future to have branches that have dependencies that are different from master, rather than having a single image with all necessary dependencies installed, which may at some point end up not being possible to do.
(cherry-picked from commit 1bb5fdf2830515d33793c52f298d305bd12b5a60)
utils/travis/install_deps.sh - no longer executes anything outside of the osx if block.
utils/travis/exit_wrapper.sh - I honestly don't know why this exists.
utils/travis/test_wrapper.sh - No longer used as of 7ca5a0df6449b4b895842566d33a38872f1f507e.
(cherry-picked from commit 344b5c56b90cffcbc9638bcb7535bb3e0f073da7)
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.
