Improve diagnostic for download_tar.
Improve diagnostic for download_tar.

ddcc/binaryen,ddcc/binaryen,WebAssembly/binaryen,ddcc/binaryen,yurydelendik/binaryen,yurydelendik/binaryen,ddcc/binaryen,yurydelendik/binaryen,WebAssembly/binaryen,ddcc/binaryen,yurydelendik/binaryen,WebAssembly/binaryen,yurydelendik/binaryen,WebAssembly/binaryen,WebAssembly/binaryen