Fix #1285 - __builtin___snprintf_chk warning. Tighten test flags and refactor the code to squash all warnings

.github/workflows/test.yml

@@ -37,4 +37,9 @@ jobs:
       run: make mingw
     - name: mingw++
       run: make mingw++
-
+  arm:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: arm
+      run: make arm