[vcpkg] Fix build.
Fixes Fixes MicrosoftDocs/vscodespaces#827.
MODIFY
src/vcpkg/vcpkgcmdarguments.cpp
src/vcpkg/vcpkgcmdarguments.cpp
@@ -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;

[vcpkg] Fix GCC-6 build. (#14616)

Fixes #13937. Fixes MicrosoftDocs/vscodespaces#827.