Update v8 architectures, cc nodejs#893

PeterDaveHello · PeterDaveHello · commit bfdf133e3cc3 · 2018-11-21T03:44:45.000+08:00
diff --git a/8/architectures b/8/architectures
@@ -1,8 +1,8 @@
 bashbrew-arch   variants
 arm32v6  alpine
 arm32v7  jessie,onbuild,slim,stretch
-arm64v8  alpine,stretch
+arm64v8  alpine,onbuild,slim,stretch
 amd64    jessie,alpine,onbuild,slim,stretch
 i386     jessie,alpine,onbuild,slim,stretch
-ppc64le  alpine,stretch
-s390x    alpine,stretch
+ppc64le  alpine,onbuild,slim,stretch
+s390x    alpine,onbuild,slim,stretch
