README.md: Refer to the essentials of Building before diving into the examples.

Having this info would have saved me some wasted times trying to figure out why the examples would not build.

Signed-off-by: Fridtjof Siebert <[email protected]>

Author: fridis

README.md

@@ -3,6 +3,9 @@
 [![Github Actions](https://github.com/libbpf/libbpf-bootstrap/actions/workflows/build.yml/badge.svg)](https://github.com/libbpf/libbpf-bootstrap/actions/workflows/build.yml)
 [![Github Actions](https://github.com/libbpf/libbpf-bootstrap/actions/workflows/build-android.yml/badge.svg)](https://github.com/libbpf/libbpf-bootstrap/actions/workflows/build-android.yml)
 
+Make sure you have cloned this repo using `--recurse-submodules` and installed the dependencies 
+before you try to build the examples.  See [Building](#Building) for details.
+
 ## minimal
 
 `minimal` is just that – a minimal practical BPF application example. It