update README.md

Added building from repo section

README.md

@@ -3,3 +3,18 @@
 `bmcd` or 'BMC Daemon' is part of the
 [BMC-Firmware](https://www.github.com/turing-machines/BMC-Firmware) and is responsible
 for hosting Restful APIs related to node management, and configuration of a Turing-Pi 2 board.
+
+## Building
+
+This package will be built as part of the buildroot firmware located
+[here](https://www.github.com/turing-machines/BMC-Firmware). If you want to
+build the the binary from this repository, we recommend to use `cargo cross`:
+
+```bash
+# install cross environment
+cargo install cross --git https://github.com/cross-rs/cross
+
+# execute cross build command for Turing-Pi target
+cross build  --target armv7-unknown-linux-gnueabi -p bmcd
+```
+