message: Add constexpr in cstring_view functions
diff: @@ -5,12 +5,12 @@ namespace vcpkg
  {
  struct cstring_view
  {
  - cstring_view(const char* cstr) : cstr(cstr) {}
  + constexpr cstring_view(const char* cstr) : cstr(cstr) {}
  cstring_view(const std::string& str) : cstr(str.c_str()) {}
  - operator const char*() const { return cstr; }
  + constexpr operator const char*() const { return cstr; }
  - const char* c_str() const { return cstr; }
  + constexpr const char* c_str() const { return cstr; }
  private:
  const char* cstr;
  @@ -20,12 +20,12 @@ namespace vcpkg
  struct cwstring_view
  {
  - cwstring_view(const wchar_t* cstr) : cstr(cstr) {}
  + constexpr cwstring_view(const wchar_t* cstr) : cstr(cstr) {}
  cwstring_view(const std::wstring& str) : cstr(str.c_str()) {}
  - operator const wchar_t*() const { return cstr; }
  + constexpr operator const wchar_t*() const { return cstr; }
  - const wchar_t* c_str() const { return cstr; }
  + constexpr const wchar_t* c_str() const { return cstr; }
  private:
  const wchar_t* cstr;
  