Fix vcpkg install to use correct architecture (arm64/x64)
as a host when using --host-triplet argument.
Pick-to: 6.11
Task-number: QTQAINFRA-7691
Change-Id: I899f6521b47e407e1c9bde1c0f2b83e560894794
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>