Add notes about static building on README.md

Author: mfontanini

README.md

@@ -62,6 +62,8 @@ cmake ..
 make
 ```
 
+## CMake options
+
 If you have installed _librdkafka_ on a non standard directory, you can use the
 `RDKAFKA_ROOT_DIR` cmake parameter when configuring the project:
 
@@ -73,6 +75,15 @@ Note that finding _librdkafka_ will succeed iff there's an _include_ and _lib_
 directories inside the specified path, including both the _rdkafka.h_ header
 and the _librdkafka_ library file.
 
+---
+
+By default, a shared library will be built. If you want to perform a static build,
+use the _CPPKAFKA_BUILD_SHARED_ parameter:
+
+```Shell
+cmake .. -DCPPKAFKA_BUILD_SHARED=0
+```
+
 # Using
 
 If you want to use _cppkafka_, you'll need to link your application with: