Third time's the charm (maybe)!

Can you remind me what the failure was last time? Xcode version issues?

Can you remind me what the failure was last time? Xcode version issues?

#73807 (comment)

Xcode 11 had an allow list VALID_ARCHS build setting which I had used before ARM was a thing to indicate that plugins shouldn't build for the 32-bit i386 simulator.
https://github.com/flutter/plugins/blob/bc2514ebd824adb1c85709e53bc57235af7b5212/packages/device_info/device_info/ios/device_info.podspec#L21

s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'VALID_ARCHS[sdk=iphonesimulator*]' => 'x86_64' }

Xcode 12 has a new EXCLUDED_ARCHS build setting which is the deny list version of VALID_ARCHS, which the plugin template now uses instead #64504. But there are plenty of plugins that use the older style VALID_ARCHS plugin template.

When both were present, Xcode 11 had a little freak out, which was the cause for the last two reverts (this took me hours to figure out).

stdout:     warning: There are no architectures to compile for because all architectures in VALID_ARCHS (x86_64) are also in EXCLUDED_ARCHS (x86_64, i386). (in target 'device_info' from project 'Pods')

That error doesn't even make sense--the EXCLUDED_ARCHS build setting in this PR doesn't contain x86_64.

But now the devicelab is on Xcode 12 and it's the minimum version the tool allows for developers. Xcode 12 handles these build settings, so with this PR even when plugins have VALID_ARCHS set, it prefers EXCLUDED_ARCHS and excludes arm64 and i386. Once the Flutter.framework ships with an arm64 simulator, we can remove arm64 from that list.