WiX Toolset v4-preview.0 is available. For more information, see Rob’s blog post on the matter.
As I mentioned before, almost all custom actions are build for all the platforms WiX v4 supports, which now includes the relatively-new (at least on Windows) ARM64 platform. Unfortunately, building ARM64 has exposed a bug in Visual Studio 2019; intermittently, but often enough to break most WiX v4 builds, the C++ compiler will crash with this oh-so-helpful error message:
LINK : fatal error LNK1318: Unexpected PDB error; RPC (23) '(0x000006BA)'
The only mild upside is that rerunning the build usually lets it run to completion. Well, at least on machine. Your results may vary.
There is a light at the end of the tunnel: Sean reported the bug to Microsoft back in May and though it was reported fixed in Visual Studio 2019 16.10, nevertheless it persisted. A new fix is available in Visual Studio 2019 16.11 Preview 2.
So, does it actually fix the problem? Yes it does! I’ve been meaning to install the Community edition of Visual Studio to verify it can build WiX v4 end to end. Installing the Preview fork of the Community edition lets me try both Preview and Community and save disk space.