Update building.md

docs/building.md

@@ -2,6 +2,20 @@
 
 # Building SGX wallet from source
 
+## Build and install Intel SGX SDK
+
+`git clone -b sgx_2.13 --depth 1 https://github.com/intel/linux-sgx`
+
+`cd linux-sgx`
+`make preparation`
+`sudo make sdk_install_pkg_no_mitigation`
+` cd /opt/intel`
+`sudo sh -c 'echo yes | /linux-sgx/linux/installer/bin/sgx_linux_x64_sdk_*.bin'`
+`sudo make psw_install_pkg
+`sudo cp /linux-sgx/linux/installer/bin/sgx_linux_x64_psw*.bin .
+`sudo ./sgx_linux_x64_psw*.bin --no-start-aesm`
+
+
 ## Clone this repository and its submodules
 
 `git clone --recurse-submodules  https://github.com/skalenetwork/sgxwallet.git`