THRIFT-3690 Work around docker image build failures on Travis-CI
Client: Build
Patch: Nobuaki Sukegawa

This closes #906
diff --git a/build/docker/scripts/cross-test.sh b/build/docker/scripts/cross-test.sh
index d9562ab..4da7813 100755
--- a/build/docker/scripts/cross-test.sh
+++ b/build/docker/scripts/cross-test.sh
@@ -3,7 +3,7 @@
 
 ./bootstrap.sh
 ./configure --enable-tutorial=no
-make -j4 precross
+make -j3 precross
 
 set +e
 make cross