Fix: Don't call locking CRT functions after fork(), as it can deadlock in musl

src/dds/proc.nix.cpp

 
 ::pid_t
 spawn_child(const std::vector<std::string>& command, int stdout_pipe, int close_me) noexcept {
+    // We must allocate BEFORE fork(), since the CRT might stumble with malloc()-related locks that
+    // are held during the fork().
+    std::vector<const char*> strings;
+    strings.reserve(command.size() + 1);
+    for (auto& s : command) {
+        strings.push_back(s.data());
+    }
+    strings.push_back(nullptr);
+
     auto child_pid = ::fork();
     if (child_pid != 0) {
         return child_pid;
     rc = dup2(stdout_pipe, STDERR_FILENO);
     check_rc(rc != -1, "Failed to dup2 stderr");
 
-    std::vector<const char*> strings;
-    strings.reserve(command.size() + 1);
-    for (auto& s : command) {
-        strings.push_back(s.data());
-    }
-    strings.push_back(nullptr);
     ::execvp(strings[0], (char* const*)strings.data());
 
     if (errno == ENOENT) {
         std::cerr
             << fmt::format("[dds child executor] The requested executable ({}) could not be found.",
                            strings[0]);
-        std::exit(-1);
+        std::quick_exit(-1);
     }
 
     std::cerr << "[dds child executor] execvp returned! This is a fatal error: "
               << std::system_category().message(errno) << '\n';
 
-    std::terminate();
+    std::quick_exit(-1);
 }
 
 }  // namespace