Fix failing MacOS 11 tests and remove obsolete build platforms

Integrated via #415

Merge branch 'chrysle:fix-macos-11-tests'

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
   test:
     strategy:
       matrix:
-        platform: [ubuntu-20.04, ubuntu-18.04, macos-11, macos-10.15]
+        platform: [ubuntu-20.04, macos-11]
     runs-on: ${{ matrix.platform }}
     steps:
     - uses: actions/checkout@v2

todo.sh

@@ -491,7 +491,8 @@ replaceOrPrepend()
 fixMissingEndOfLine()
 {
     # Parameters:    $1: todo file; empty means $TODO_FILE.
-    sed -i.bak -e '$a\' "${1:-$TODO_FILE}"
+    todo_path="${1:-$TODO_FILE}"
+    [[ -f $todo_path && $(tail -c1 "$todo_path") ]] && echo "" >> "$todo_path"    
 }
 
 uppercasePriority()