Comment 7 for bug 1873406

The situation on plain Windows is very similar.
On a 64bit Windows system (the standard) running the vcvarsall.bat tool sets up your shell for using the 32bit or 64bit native Visual Studio compiler.
In this case, again, there is no cross compiling involved. It's either the 32bit compiler producing executables for 32bit or the 64bit compiler producing 64bit executables. (You could also set up cross compiling 32->64 or 64->32, but that's a separate topic.)

Even after you have run vcvarsall.bat setting up everything for 32bit native compiling, EpicsHostArch will report that the architecture is 'windows-x64'. Which is technically correct, but clearly and obviously not the architecture that you want EPICS to use.
(This is the situation for all our CI builds, where we first run vcvarsall.bat and after that still can't use the EpicsHostArch script.)