[clang][SYCL] Set default device and host triples for SYCL device compilation (#172366)
This PR checks whether the triple specified for SYCL device compilation
is supported. If the triple is not specified, assume a default of
spirv64-unknown-unknown.
While a driver invocation does set the default triple when invoked, this
PR is required to fix a crash for cc1 invocations when an invalid/no
triple is specified.
This PR also sets HostTriple from -aux-triple to inherit host type
properties during SYCL device compilation.
Fixes https://github.com/llvm/llvm-project/issues/167358