Update build

Readme.md

@@ -1,16 +1,11 @@
 # how to build
 ```
 g++ build.cpp -o build
-```
-
-after first emsdk clone run this
-
-```
-cd emsdk
-./emsdk install latest
-./emsdk activate latest
-source ./emsdk_env.sh
-cd ..
+./build
+or 
+./build run
+or
+./build cla build web // first clear all then build for web
 ```
 
 # Code style