Try to forcefully kill all child processes on Windows

Author: polytypic

travis-ci

@@ -111,6 +111,9 @@ if [ "$TRAVIS_OS_NAME" = windows ]; then
   for CONFIG in Debug Release; do
     CMAKE_BUILD_TYPE=$CONFIG CC='' CXX='' CMAKE_GENERATOR="Visual Studio 16 2019" folded "VC2019 $CONFIG" cppsm test
   done
+
+  # shellcheck disable=2009,2046
+  kill -9 $(ps | grep -o "^ *[0-9]\\+  *$$ " | sed -e 's#^ *##g' -e 's# .*##g') 2>/dev/null || true
 fi
 
 code-coverage() {