Add --as-needed to linker command line
Add --as-needed to linker command line

For some reason this is the default for g++ but not clang++. Without
this, some LLVM library is injecting extra cl:: args that make
sexpr-dump require extra positional args.

dschuff/WAOT,WebAssembly/wasm-aot-prototype,WebAssembly/wasm-aot-prototype,dschuff/WAOT,dschuff/WAOT,WebAssembly/wasm-aot-prototype