add linux board project

board/Linux_Posix/hello_world/readme.md

@@ -0,0 +1,36 @@
+# How to run the demo in linux
+
+## step1
+make sure your develop environment.
++ `cmake` and version greater than 3.8.2
++ `gcc` `gdb` `make` is installed
+
+## step2
+make `build` directory and compile in `build`
+
+```bash
+mkdir build && cd build
+cmake ..
+make
+```
+
+## step3
+run program !!
+
+```bash
+# in build directory
+./hello_world
+```
+
+## other
+you can copy this demo to other path, but if you want do it,
+you need modify `CMakeLists.txt`. find line
+
+```cmake
+set(TINY_ROOT ../../../)
+```
+
+and modify `path-to-tinyos`
+```cmake
+set(TINY_ROOT path-to-tinyos)
+```