message: Add home_dir impl for Windows UWP platforms
diff: @@ -18,7 +18,12 @@ use winapi::um::winnt::TOKEN_READ;
  pub fn home_dir_inner() -> Option<PathBuf> {
  env::var_os("USERPROFILE")
  .map(PathBuf::from)
  - .or_else(|| unsafe {
  + .or_else(|| home_dir_crt())
  +}
  +
  +#[cfg(not(target_vendor = "uwp"))]
  +fn home_dir_crt() -> Option<PathBuf> {
  + unsafe {
  let me = GetCurrentProcess();
  let mut token = ptr::null_mut();
  if OpenProcessToken(me, TOKEN_READ, &mut token) == 0 {
  @@ -38,7 +43,12 @@ pub fn home_dir_inner() -> Option<PathBuf> {
  os2path,
  )
  .ok()
  - })
  + }
  +}
  +
  +#[cfg(target_vendor = "uwp")]
  +fn home_dir_crt() -> Option<PathBuf> {
  + None
  }
  fn os2path(s: &[u16]) -> PathBuf {
  