adding a makefile target for creating bin directory in all samplecode

This error seems existed in all samplecode now.
It is caused by
https://github.com/baidu/rust-sgx-sdk/blob/cb4cfb029bc5329d2fdefc18b0c1b656012bc873/.gitignore#L22
I hadn't found it when I wrote it.

The solution is provided by @akoskinas https://github.com/baidu/rust-sgx-sdk/pull/120

Maybe we could tag a `help wanted` and `good first issue`? @dingelish

Start by reviewing the linked .gitignore entry at line 22 and the solution in pull request #120. Check how the Makefiles are organized across the samplecode directories, then verify that the proposed target creates the bin directory and resolves the reported error in all samples.

Written by the indexing model from the issue text.