asm.js binaries in bin/ and wasm binaries in wasm/

[cameel]

Depends on on #38. Part of ethereum/solidity#9258.

Currently bin/ contains a mix of wasm and asm.js binaries. This makes it hard to determine where an older release downloaded from github would go. This PR moves all wasm binaries from bin/ to wasm/ and adds symlinks in their place.

This required changing the update script to make it not ignore the newly added symlinks.

[cameel]

Here's the script I used to separate the files:

#!/usr/bin/env bash

set -e

is_wasm() {
    # Just a heuristic but it does match the expected release versions in solc-bin so far.
    grep --fixed-strings --silent 'var wasmBinaryFile="data:application/octet-stream;base64,AGFzbQEA' "$@" && return 0
    return 1
}

for src_dir in bin wasm; do
    cd "$src_dir"
    for binary_name in $(find * -regex 'soljson-v[0-9.]+\+commit\..*\.js' -type f | sort); do
        full_version=$(echo "$binary_name" | sed -r 's/soljson-(v[0-9.]+\+commit\..*)\.js/\1/')

        if is_wasm "$binary_name"; then
            if [[ $src_dir == bin ]]; then
                echo "Moving wasm binary bin/${binary_name} to wasm/"
                dst_dir="wasm"
            else
                continue
            fi
        else
            if [[ $src_dir == wasm ]]; then
                echo "Moving asm.js binary wasm/${binary_name} to bin/"
                dst_dir="bin"
            else
                continue
            fi
        fi

        if [[ -e "../${dst_dir}/${binary_name}" ]]; then
            [[ -L "../${dst_dir}/${binary_name}" ]] || { echo "ERROR: File ${dst_dir}/${binary_name} already exists and is not a symbolic link"; exit 1; }
            rm "../${dst_dir}/${binary_name}"
        fi

        mv "$binary_name" "../${dst_dir}/${binary_name}"
        ln --symbolic "../${dst_dir}/${binary_name}" "$binary_name"
    done
    cd ..
done