I don’t use CMake either. You only have to edit one file in the Projucer project (jucer_ProjectExport_Xcode.h) following the diff posted by yairadix here: AAX + XCode 12 Unknown Platform/OS/Compiler workaround + FR - #10 by yairadix
In this way you don’t have to manually change your XCode project every time you resave the jucer file.
The manual XCode change I posted above is only needed to build the AAX SDK on Big Sur.
@ed95 Can we have Yair’s fix on master please, at least until AAX is known to work for silicon / arm chips too?
By the way: I really love you guys and appreciate all the hard work you have been / are doing for all of us in maintaining and extending JUCE, so that we can focus on other things 
However it worries me a little bit that this is currently still an issue on master. Does that mean that there are no tests being done for AAX plugins with master at the moment? Because this should pop up right away during a plugin AAX build, no?
A. Even without it, AAX debug would compile when set to Intel.
B. For release I’m able to build on vanilla JUCE just by building each target by itself and enforcing AAX arch.
C. Avid has a patch available for testing in their developer area.
Yes, I’ve used the valid architectures setting in the Projucer to restrict the build to only Intel for now and that works. I’ll get back to universal binaries for VST/AU (and eventually AAX) later.
That build script you pointed to looks very useful, thanks!
I had a quick look at that AAX code patch but will hold off a little longer for now.
Thanks for the feedback and help!
Just started faffing about with AAX again (argh!), and ran into this ARM incompatibility nonsense (very argh!). I really wish this landed on the mainline; newcomers (revisitors like myself?) will continue running into this till the heel dragging on Avid’s part is gone.
TL;DR Avid has a patch (in that post) which you are only supposed to use for testing, and the work is underway for AAX to operate fine on Apple Silicon.
That’s great, but who knows the timeline for a proper AAX SDK update. Till then… see my post above.
This is a great thread, unfortunately, I still can’t compile AAX using Big Sur and Xcode 12.5.1
Here is a screenshot of the settings, it accepts x86_64 but then translates it to the following:-
I can give you our command line build which I think is good enough:
ADDITIONAL_FLAGS="GCC_TREAT_WARNINGS_AS_ERRORS=NO -UseModernBuildSystem=NO"
xcodebuild -project $AAX_SDK_PATH/Libs/AAXLibrary/MacBuild/AAXLibrary.xcodeproj -target "AAXLibrary_libcpp" -configuration "Debug" ARCHS="x86_64" OTHERCFLAGS="-Wpragma-pack -Werror" ${ADDITIONAL_FLAGS}
please mind this is Debug and you’d also like to build release with similar manner 
Thanks, I will try that.
I just noticed it compiled OK if select ‘Build Active Architecture Only : YES’
But I don’t understand why it wanted to compile anything else, from the options.