update: adding more local build details to the README.md (#1022)

Author: antitree

README.md

@@ -121,10 +121,37 @@ Requirements:
 * [rust](https://www.rust-lang.org) - yara-x requirement
 * [yara-x](https://virustotal.github.io/yara-x/) - Rust implementation of YARA
 * [pkgconf](http://pkgconf.org/) - required by Go to find C dependencies, included in many UNIX distributions
+* [libssl-dev](https://packages.debian.org/buster/libssl-dev) package
 
 To install yara-x, first install Rust and then run `make install-yara-x` which will clone the yara-x repository and install yara-x's dependenicies and its C API.
 
-For more information about the yara-x C API, reference the documentation here: https://virustotal.github.io/yara-x/docs/api/c/c-/#building-the-c-library.
+### Building locally in Debian/Ubuntu
+
+1. Install the dependencies. On Debian/Ubuntu you can run:
+
+   ```bash
+   sudo apt-get install -y pkgconf libssl-dev
+   ```
+   
+   Make sure [Go](https://go.dev/doc/install) and [Rust](https://www.rust-lang.org/tools/install) are installed
+
+2. Run `make install-yara-x` to build the yara-x C API. (The
+   `yara_xcapi.pc` file will be generated under `./out/lib/pkgconfig`. 
+   For more information about the yara-x C API, reference the documentation here: https://virustotal.github.io/yara-x/docs/api/c/c-/#building-the-c-library.).
+
+3. Build the malcontent binary with:
+
+   ```bash
+   make out/mal
+   ```
+
+   The resulting binary is `out/mal`.
+
+4. OPTIONAL: Install the binary
+
+  ```bash
+  sudo install out/mal /usr/local/bin
+  ```
 
 ## Help Wanted