Replace travis with github actions (#9641)

* Move outside of travis to Github actions

This will permit to have better integrated CI workflow than the previous
travis one.

util/ci/clang-tidy.sh

@@ -0,0 +1,18 @@
+#! /bin/bash -eu
+
+mkdir -p cmakebuild
+cd cmakebuild
+cmake -DCMAKE_BUILD_TYPE=Debug \
+	-DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
+	-DRUN_IN_PLACE=TRUE \
+	-DENABLE_GETTEXT=TRUE \
+	-DENABLE_SOUND=FALSE \
+	-DBUILD_SERVER=TRUE ..
+make GenerateVersion
+
+cd ..
+
+./util/ci/run-clang-tidy.py \
+	-clang-tidy-binary=clang-tidy-9 -p cmakebuild \
+	-quiet -config="$(cat .clang-tidy)" \
+	'src/.*'