Back in the early days of Yeppp! it supported cross-compilation for Windows on ARM.
However, after Microsoft announced that WinAPI won't be available on WinRT, support was dropped.
I have no plans to implement it again, but if you're willing to contribute WinRT support, I am positive about merging it to the main repo.
The main issue with WinRT support is that PeachPy (the assembly generator for Yeppp!) currently emits ARM assembly only in GNU format, which is incompatible with Microsoft ARM assembler.
Regards,
Marat