UserspaceEmulator: Implement the getsid() syscall

DevTools/UserspaceEmulator/Emulator.cpp

@@ -293,6 +293,8 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
         return virt$gettid();
     case SC_getpid:
         return virt$getpid();
+    case SC_getsid:
+        return virt$getsid(arg1);
     case SC_pledge:
         return virt$pledge(arg1);
     case SC_unveil:
@@ -1325,6 +1327,11 @@ int Emulator::virt$getcwd(FlatPtr buffer, size_t buffer_size)
     return rc;
 }
 
+int Emulator::virt$getsid(pid_t pid)
+{
+    return syscall(SC_getsid, pid);
+}
+
 int Emulator::virt$access(FlatPtr path, size_t path_length, int type)
 {
     auto host_path = mmu().copy_buffer_from_vm(path, path_length);