This environment variable is used by vcpkg to avoid having to pass the --triplet argument on the command line on every vcpkg invocation and shouldn't influence the triplet used during build. In fact, the vcpkg.cmake toolchain will automatically attempt to deduce the target triplet if we don't define this beforehand. As a replacement, read from the QT_VCPKG_TARGET_TRIPLET environment variable. It has the QT_ prefix to make it clear this is not a standard vcpkg environment variable. [ChangeLog][Build System] Qt no longer uses the VCPKG_DEFAULT_TRIPLET environment variable to deduce target triplet. By default we let vcpkg's toolchain file automatically deduce the triplet to use. The new QT_VCPKG_TARGET_TRIPLET environment variable can be used instead, or pass -DVCPKG_TARGET_TRIPLET=<triplet> to CMake. Pick-to: 6.6 Change-Id: Idc6cbd52a68578d1762ca175c4973355409688ac Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io> Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>