Rsync files to VM rather than sync folders, since sync folders was causing clock skew and confusig make.

.gitignore

@@ -33,3 +33,4 @@ tags
 java/*.log
 java/include/org_rocksdb_*.h
 unity.cc
+java/crossbuild/.vagrant

java/crossbuild/Vagrantfile

@@ -9,17 +9,17 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
   config.vm.define "linux32" do |linux32|
     linux32.vm.box = "ubuntu/trusty32"
     linux32.vm.provision :shell, path: "build-linux.sh"
-    linux32.vm.synced_folder "../..", "/rocksdb"
   end
 
   config.vm.define "linux64" do |linux64|
     linux64.vm.box = "ubuntu/trusty64"
     linux64.vm.provision :shell, path: "build-linux.sh"
-    linux64.vm.synced_folder "../..", "/rocksdb"
   end
 
   config.vm.provider "virtualbox" do |v|
     v.memory = 2048
     v.cpus = 4
   end
+
+  config.vm.synced_folder "../..", "/rocksdb", type: "rsync"
 end