Fix usage of wrong string type in os.execute

[PRTTMPRPHT]

Hello there,

I noticed that os.execute is currently broken (tested with node v15.0.1).
The string fed into the implementation is actually a lua string (passed as an Uint8Array).
This needs to be converted to a normal JS string, as otherwise, exec will reject the input with the following error message:

The "file" argument must be of type string. Received an instance of Uint8Array

Here is a quick&dirty sample script to test this:

const {lauxlib, lua, lualib, to_jsstring, to_luastring} = require("fengari");

let L = lauxlib.luaL_newstate();
lualib.luaL_openlibs(L);

const luaSource = to_luastring("return os.execute('hostname')");

const exitCode = lauxlib.luaL_dostring(L, luaSource);

if (exitCode !== 0) {
    const errorMessage = lua.lua_tostring(L, -1);
    console.log("Error:", to_jsstring(errorMessage));
    return;
}

console.log(to_jsstring(lua.lua_tostring(L, -1)));

With the proposed fix, it will output the hostname correctly.

[sonarcloud]

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0 Bugs
0 Vulnerabilities
0 Security Hotspots
8 Code Smells

No Coverage information
0.0% Duplication

[daurnimator]

Thanks!