Remove some unsupport system call for WASM

Signed-off-by: Le Yao <le.yao@intel.com>

Author: Le Yao

README.md

@@ -20,6 +20,11 @@ and applying traditional ModSecurity processing. In general, it provides the
 capability to load/interpret rules written in the ModSecurity SecRules format
 and apply them to HTTP content provided by your application via Connectors.
 
+# Build ModSecurity WASM library
+
+Please read this [guide]() to build your own wasm library using Emscripten.
+
+
 If you are looking for ModSecurity for Apache (aka ModSecurity v2.x), it is still under maintenance and available:
 [here](https://github.com/SpiderLabs/ModSecurity/tree/v2/master).