bump pbuild datasize limit to 8G to allow Firefox to build with Rust 1.44

ok deraadt@

src/etc/etc.amd64/login.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: login.conf,v 1.15 2020/05/23 13:16:03 danj Exp $
+# $OpenBSD: login.conf,v 1.16 2020/06/23 15:45:34 naddy Exp $
 
 #
 # Sample login.conf file.  See login.conf(5) for details.
@@ -91,7 +91,7 @@ authpf:\
 #
 pbuild:\
 	:datasize-max=infinity:\
-	:datasize-cur=7168M:\
+	:datasize-cur=8192M:\
 	:maxproc-max=1024:\
 	:maxproc-cur=384:\
 	:priority=5:\