Fix for future versions of python (#911)

Starting python 3.10, the use of - instead of _ will get a warn (see https://bugs.gentoo.org/796281 for reference)

Signed-off-by: Marco Scardovi <marco@scardovi.com>
diff --git a/setup.cfg b/setup.cfg
index 990b9e1..16da438 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,5 @@
 [build]
-build-base=bin
+build_base=bin
 
 [yapf]
 based_on_style=google