bpo-43244: Fix test_peg_generators on Windows (GH-24913)
Don't redefine Py_DebugFlag, it's already defined in pydebug.h which
is included by Python.h
diff --git a/Parser/parser.c b/Parser/parser.c
index acfaf80..6efaebe 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -2,10 +2,9 @@
#include "pegen.h"
#if defined(Py_DEBUG) && defined(Py_BUILD_CORE)
-extern int Py_DebugFlag;
-#define D(x) if (Py_DebugFlag) x;
+# define D(x) if (Py_DebugFlag) x;
#else
-#define D(x)
+# define D(x)
#endif
static const int n_keyword_lists = 9;
static KeywordToken *reserved_keywords[] = {