Travis: Actually use gcc on OS X
On macOS, gcc is an alias to clang:
GCC version
Apple LLVM version 9.1.0 (clang-902.0.39.2)
Target: x86_64-apple-darwin17.4.0
Thread model: posix
InstalledDir: /Applications/Xcode-9.4.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
https://travis-ci.org/teor2345/tor/jobs/421941946#L35
Doc update: https://github.com/travis-ci/docs-travis-ci-com/pull/2002
If we want to use gcc on OS X, we have to set a specific GCC version in the environmental variables: https://docs.travis-ci.com/user/languages/c/#gcc-on-os-x
Edit: canonical URL