message: [vcpkg] Fix build.
  Fixes Fixes MicrosoftDocs/vscodespaces#827.
diff: @@ -920,6 +920,7 @@ namespace vcpkg
  constexpr StringLiteral VcpkgCmdArguments::TRIPLET_ARG;
  constexpr StringLiteral VcpkgCmdArguments::OVERLAY_PORTS_ENV;
  constexpr StringLiteral VcpkgCmdArguments::OVERLAY_PORTS_ARG;
  + constexpr StringLiteral VcpkgCmdArguments::OVERLAY_TRIPLETS_ENV;
  constexpr StringLiteral VcpkgCmdArguments::OVERLAY_TRIPLETS_ARG;
  constexpr StringLiteral VcpkgCmdArguments::OVERLAY_TRIPLETS_ENV;
  