Modify the build-wheels.sh to build_wheels.sh

The path is tools/build_wheels.sh, but in the Makefile which is
tools/build-wheels.sh. Modify it to the correct one.

Change-Id: If297b65b539403af10a73adbbadfcd8281d40009
Closes-Bug: #1507699
diff --git a/Makefile b/Makefile
index 082aff2..a6bb230 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@
 	./unstack.sh
 
 wheels:
-	WHEELHOUSE=$(WHEELHOUSE) tools/build-wheels.sh
+	WHEELHOUSE=$(WHEELHOUSE) tools/build_wheels.sh
 
 docs:
 	tox -edocs