The Travis configuration:
1) Installs recent versions of clang and GCC.
2) Sets up the environment so that CMake picks up the installed
compilers. Previously, the pre-installed clang compiler was used
instead.
3) Requests a modern macOS image that has all the headers needed by GCC.
The CL also removes now-unnecessary old workarounds from the
Travis configuration.
PiperOrigin-RevId: 245831188
This CL fixes the following issues:
* The Travis CI had the ctest invocation followed by a ";", so non-zero
exit codes (indicating test failures) did not cause the build to fail.
* The AppVeyor CI had the ctest invocation followed by a ";", causing an
error on Windows, where "&" plays the role of ";" [1].
The Windows CI (AppVeyor) will still be red after this CL, as some of
the tests are failing. However, this CL is a step forward, as it gets us
from failing to start tests to running tests and recording success/error
states.
[1] https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490954(v=technet.10)#using-multiple-commands-and-conditional-processing-symbols
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=236765633
This aligns the Travis CI configuration with google/crc32c and
google/snappy, to simplify maintenance.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188547648
