Fix detection of copyright tools

CC #104

src/core/copyright/copyright.cpp

@@ -11,17 +11,36 @@ namespace linuxdeploy {
             using namespace log;
 
             std::shared_ptr<ICopyrightFilesManager> ICopyrightFilesManager::getInstance() {
-                auto check_command = [](const std::string& command) {
-                    auto p = subprocess::Popen(
-                        command,
-                        subprocess::output(subprocess::PIPE),
-                        subprocess::error(subprocess::PIPE)
-                    );
+                // very simple but for our purposes good enough which like algorithm to find binaries in $PATH
+                // TODO: move into separate function to be used in the entire code base
+                // FIXME: remove dependency on subprocess library
+                static const auto which = [](const std::string& name) -> bf::path {
+                    const auto* path = getenv("PATH");
 
-                    return p.wait();
+                    if (path == nullptr)
+                        return "";
+
+                    for (const auto& binDir : subprocess::util::split(path, ":")) {
+                        if (!bf::is_directory(binDir)) {
+                            continue;
+                        }
+
+                        for (bf::directory_iterator it(binDir); it != bf::directory_iterator{}; ++it) {
+                            const auto binary = it->path();
+
+                            std::cout << binary << std::endl;
+
+                            if (binary.filename() == name) {
+                                // TODO: check if file is executable (skip otherwise)
+                                return binary;
+                            }
+                        }
+                    }
+
+                    return {};
                 };
 
-                if (check_command("command -v dpkg-query") == 0) {
+                if (!which("dpkg-query").empty()) {
                     ldLog() << LD_DEBUG << "Using dpkg-query to search for copyright files" << std::endl;
                     return std::make_shared<DpkgQueryCopyrightFilesManager>();
                 }