Hello Anthony

The first log you posted looks like a compiler crash. Unfortunately I no longer provide my own builds of Clang/LLVM and Swift, the builder now uses the official ones - I thought it would save me much time and the builds would be more stable (bottom line: I was half right...), so my ability to fix this crash has dropped to not much: a bug report should be submitted to the official Swift maintainers, who usually don't prioritize much their rare Windows users.

The second log looks like as if a non-ASCII character, or a control character, was passed in the linker's command line, and that would make the command-line interpreter jump off track. You might get confirmation of that if you run the build in verbose mode (hold the Shift key down when you click the Build button). Examples of such characters include parentheses "(", ")", in directory names, ampersands "&", percent signs "%" or carets "^". Such characters easily divert a batch script. If one of your project's file names or directory names has such a character in it, rename it.

The third log does look like the same crash as the first one.

"iOS Build Environment" is the old name for "Darwin Build Environment" - it was renamed to "Darwin" since now it also builds Mac apps and not just iOS. And it's a superset of the "Project Builder for Unity" which you are certainly using since you're asking the question. You don't need it if all your builds are Unity projects.

It looks like this version of the "AppAuth" pod makes the compiler crash. To work this around, consider using precompiled versions of these libraries and frameworks instead of trying to build them from source with CocoaPods.

Another thing you can try is to download the most up-to-date version of the Win32 variant of the official Swift compiler binary distribution (which includes the Clang compiler and the LLVM tools), and replace the executables and DLLs in the Toolchain directory of the builder with the ones you downloaded. It is possible that they fixed this very crash bug. Make a backup of the Toolchain directory before you try that.

This error you get with the Swift-supplied LDD is an irrelevant limitation they put on the Swift version of LLD. It has been classified as a "bug" for a long time, and I see they still haven't taken any step to remove it. This alone tells a lot how much they care about Windows users.

To get rid of it, download and install the corresponding LLD from the official LLVM builds (not Swift). The LLD linker is exactly the same in both distributions.

I see that AppAuth doesn't seem to provide precompiled libraries nor frameworks. They could, and IMO should. In this case, what you can do is build these files on Mac, and reuse them in your project, either as a static library, or a framework, by specifying the precompiled file in the extra linker flags. Do you need help on that ?