Add news file explaining the new pip wheel behavior

sbidoul · sbidoul · commit 1ef342dd07e2 · 2019-12-28T16:13:57.000+01:00
diff --git a/news/7517.feature b/news/7517.feature
@@ -0,0 +1,4 @@
+The build step of ``pip wheel`` now builds all wheels to a cache first,
+then copies them to the wheel directory all at once.
+Before, it built them to a temporary direcory and moved
+them to the wheel directory one by one.
