Cross compile bundled dependencies

- This commit changes the bundled deps build recipes to work with
  a cross compiler (tested w/ mingw in Linux)
- Move build recipes for libuv, luajit, msgpack and luarocks into
  separate files
- Build luajit twice for the host/target platform
- Adjust CMake search path when cross compiling using bundled deps
- Search for HOST executables in .deps/host
- Added new variable in third-party/CMakeLists.txt
  DEPS_HOST_INSTALL_DIR - to be used for dependencies targetting
  the host