Add a cross-file for MSVC UWP ARM64.
Bump cidata tag to get an updated install.ps1 script (run by run.ps1)
which sets the vcvars environment correctly when cross-compiling.
Since arranging the correct environment for simultaneous cross and
native 'cl' use is hard, this is test run uses '--cross-only' so we
don't require a native compiler.
Extend '--cross-only' so it also explicitly uses a machine file which
makes all build machine compilers unusable.
Jon Turney