Add build flag to disable build of libwasm (#1435)
Add build flag to disable build of libwasm (#1435)

This allows the wabt tools to be build with no git submodules
WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt