Update OVMF build instructions
@@ -74,6 +74,8 @@ when no macOS guest booting is required.
1. Build OVMF firmware in NOOPT mode to be able to debug it:
```
+ git submodule init
+ git submodule update # to clone OpenSSL
build -a X64 -t XCODE5 -b NOOPT -p OvmfPkg/OvmfPkgX64.dsc # for macOS
build -a X64 -t CLANGPDB -b NOOPT -p OvmfPkg/OvmfPkgX64.dsc # for other systems
```
