doc/build_wasm_app.md: Update a note about LLVM 13 incompatibility (#1441)
doc/build_wasm_app.md: Update a note about LLVM 13 incompatibility (#1441)

Remove the workaround as it wasn't so good.
  (It can cause the lack of ctor calls)
Mention that it's only about a command.
bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime