Remove hacky subprocess call in action.yml (#3226)

Updates action.yml to use the alternative $GITHUB_ACTION_PATH variable
instead of the original ${{ github.action_path }} which caused issues
with bash on the Windows runners. This removes the need for a Python
subprocess to call the main.py script.

Author: ionite34

AUTHORS.md

@@ -79,6 +79,7 @@ Multiple contributions by:
 - [Hugo Barrera](mailto::[email protected])
 - Hugo van Kemenade
 - [Hynek Schlawack](mailto:[email protected])
+- [Ionite](mailto:[email protected])
 - [Ivan Katanić](mailto:[email protected])
 - [Jakub Kadlubiec](mailto:[email protected])
 - [Jakub Warczarek](mailto:[email protected])

action.yml

@@ -29,25 +29,10 @@ runs:
   using: composite
   steps:
     - run: |
-        # Exists since using github.action_path + path to main script doesn't work because bash
-        # interprets the backslashes in github.action_path (which are used when the runner OS
-        # is Windows) destroying the path to the target file.
-        #
-        # Also semicolons are necessary because I can't get the newlines to work
-        entrypoint="import sys;
-        import subprocess;
-        from pathlib import Path;
-
-        MAIN_SCRIPT = Path(r'${GITHUB_ACTION_PATH}') / 'action' / 'main.py';
-
-        proc = subprocess.run([sys.executable, str(MAIN_SCRIPT)]);
-        sys.exit(proc.returncode)
-        "
-
         if [ "$RUNNER_OS" == "Windows" ]; then
-          echo $entrypoint | python
+          python $GITHUB_ACTION_PATH/action/main.py
         else
-          echo $entrypoint | python3
+          python3 $GITHUB_ACTION_PATH/action/main.py
         fi
       env:
         # TODO: Remove once https://github.com/actions/runner/issues/665 is fixed.