build: fix error "<unknown>:51: SyntaxWarning: invalid escape sequence '\.'"

Author: thebaptiste

fastentrypoints.py

@@ -48,7 +48,7 @@
 from {0} import {1}
 
 if __name__ == '__main__':
-    sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
+    sys.argv[0] = re.sub(r'(-script\\.pyw?|\\.exe)?$', '', sys.argv[0])
     sys.exit({2}())'''  # noqa: W605