Fix RUN_THIS.py so it would be cross-platform and it would be possibl…

…e to use it from cmd on Windows (#26017)

Fix RUN_THIS.py so it would be possible to use it from cmd on Windows

RUN_THIS.py

@@ -5,14 +5,9 @@
 import sys
 import subprocess
 
-IS_WINDOWS = sys.platform in ("win32", "cygwin")
-
 version = sys.version_info
 if version.major < 3 or (version.major == 3 and version.minor < 5):
     print("ERROR: You need at least Python 3.5 to build SS14.")
     sys.exit(1)
 
-if IS_WINDOWS:
-    subprocess.run(["py", "-3", "git_helper.py"], cwd="BuildChecker")
-else:
-    subprocess.run(["python3", "git_helper.py"], cwd="BuildChecker")
+subprocess.run([sys.executable, "git_helper.py"], cwd="BuildChecker")