message: Use Strings::ascii_to_lowercase()
diff: #include "pch.h"
  #include "triplet.h"
  #include "vcpkg_Checks.h"
  +#include "vcpkg_Strings.h"
  namespace vcpkg
  {
  @@ -37,9 +38,7 @@ namespace vcpkg
  triplet triplet::from_canonical_name(const std::string& triplet_as_string)
  {
  - std::string s(triplet_as_string);
  - std::transform(s.begin(), s.end(), s.begin(), ::tolower);
  -
  + const std::string s(Strings::ascii_to_lowercase(triplet_as_string));
  auto it = std::find(s.cbegin(), s.cend(), '-');
  Checks::check_exit(it != s.cend(), "Invalid triplet: %s", triplet_as_string);
  