common/travis/build.sh: only error out if xbps-src exits with 1.

broken/nocross exits with 2, should be treated as success.

common/travis/build.sh

@@ -7,6 +7,7 @@ if [ "$1" != x86_64 ]; then
 fi
 
 for pkg in $(cat /tmp/templates); do
-	./xbps-src $arch -C pkg "$pkg" || exit 1
+	./xbps-src $arch -C pkg "$pkg"
+	[ $? -eq 1 ] && exit 1
 done