common : add getpwuid fallback for HF cache when HOME is not set

[angt]

Overview

Like llama's cache, we need a fallback when HOME is not defined, mostly thanks to systemd.

Additional information

We don't need to check for __EMSCRIPTEN__:

$ cat test.cpp
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <filesystem>

#include <unistd.h>
#include <pwd.h>

namespace fs = std::filesystem;

int main() {
    const char * home = std::getenv("HOME");
    std::cout << "HOME: " << home << std::endl;

    fs::path file = fs::path(home) / "test.txt";

    std::ofstream out(file);
    out << "something" << std::endl;
    out.close();

    std::ifstream in(file);
    std::string line;

    while (std::getline(in, line)) {
        std::cout << line << std::endl;
    }

    fs::remove(file);
    return 0;
}

$ emcc -std=c++17 test.cpp

$ node a.out.js
HOME: /home/web_user
something

If it's ok i can update fs_get_cache_directory after.

• I have read and agree with the contributing guidelines
• AI usage disclosure: NO