THRIFT-4328: split binary cross tests into their own build job to resolve
timeouts in travis; enable newly reliable cross tests (ran 5 times clean)

This closes #1351
diff --git a/build/docker/ubuntu-xenial/Dockerfile b/build/docker/ubuntu-xenial/Dockerfile
index 6324ec2..61ba5ff 100644
--- a/build/docker/ubuntu-xenial/Dockerfile
+++ b/build/docker/ubuntu-xenial/Dockerfile
@@ -141,7 +141,8 @@
       neko-dev \
       libneko0
 RUN haxelib setup --always /usr/share/haxe/lib && \
-    haxelib install --always hxcpp
+    haxelib install --always hxcpp 3.4.64
+# note: hxcpp 3.4.185 (latest) no longer ships static libraries, and caused a build failure
 
 RUN apt-get install -y --no-install-recommends \
 `# Java dependencies` \