Error: unknown type name 'FMT_NO_UNIQUE_ADDRESS'

[KellanClark]

I noticed recently that fmt was causing errors and preventing my project from compiling. The stream of errors is very long, but they all stem from

[build] In file included from C:/Users/Kellan/CLionProjects/ortin/modules/fmt/src/os.cc:13:
[build] In file included from C:/Users/Kellan/CLionProjects/ortin/modules/fmt/include\fmt/os.h:20:
[build] C:/Users/Kellan/CLionProjects/ortin/modules/fmt/include\fmt/format.h:935:3: error: unknown type name 'FMT_NO_UNIQUE_ADDRESS'
[build]   FMT_NO_UNIQUE_ADDRESS Allocator alloc_;
[build]   ^
[build] C:/Users/Kellan/CLionProjects/ortin/modules/fmt/include\fmt/format.h:935:25: warning: declaration of 'Allocator' shadows template parameter [-Wmicrosoft-template-shadow]
[build]   FMT_NO_UNIQUE_ADDRESS Allocator alloc_;
[build]                         ^
[build] C:/Users/Kellan/CLionProjects/ortin/modules/fmt/include\fmt/format.h:929:20: note: template parameter is declared here
[build]           typename Allocator = std::allocator<T>>
[build]                    ^

I bisected and found #3485 was the culprit. There's a couple confusing things about this error.

1. FMT_NO_UNIQUE_ADDRESS should be defined. It's further up in the file and my IDE shows it should expand to [[no_unique_address]] in my environment. For some reason, it's not getting replaced by the preprocessor.
2. I can't replicate this in Godbolt. It may be that I'm using the GNU command line version of Clang 15.0.1 installed by Visual Studio (not clang-cl, the clang.exe installed with it), which isn't an option.

[phprus]

@KellanClark
Test PR #3493 please.

[KellanClark]

Your PR fixes it. Thanks!