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.

.github/workflows/lua_lint.yml

@@ -0,0 +1,32 @@
+name: lua_lint
+
+# Lint on lua changes on builtin or if workflow changed
+on:
+  push:
+    paths:
+      - 'builtin/**.lua'
+      - '.github/workflows/**.yml'
+  pull_request:
+    paths:
+      - 'builtin/**.lua'
+      - '.github/workflows/**.yml'
+
+jobs:
+  luacheck:
+    runs-on: ubuntu-18.04
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install luarocks
+      run: |
+        sudo apt-get update -qyy
+        sudo apt-get install luarocks -qyy
+
+    - name: Install luarocks tools
+      run: |
+        luarocks install --local luacheck
+        luarocks install --local busted
+
+    - name: Run checks
+      run: |
+        $HOME/.luarocks/bin/luacheck builtin
+        $HOME/.luarocks/bin/busted builtin