Issue #13150: sysconfig no longer parses the Makefile and config.h files
when imported, instead doing it at build time.  This makes importing
sysconfig faster and reduces Python startup time by 20%.
diff --git a/.hgignore b/.hgignore
index 80ac2ed..0fd8562 100644
--- a/.hgignore
+++ b/.hgignore
@@ -49,6 +49,7 @@
 *.pyd
 *.cover
 *~
+Lib/_sysconfigdata.py
 Lib/lib2to3/*.pickle
 Lib/test/data/*
 Misc/*.wpu