fix: if MARKETING_VERSION or CURRENT_PROJECT_VERSION is overridden in Xcode project, pubspec version is ignored

[bryanoltman]

Description

Xcode project files contain the MARKETING_VERSION and CURRENT_PROJECT_VERSION variables that override the version and build number, respectively, in the Info.plist (and, by extension, the pubspec.yaml).

These are set by typing version and build number into Xcode directly:

and are reflected in the project.pbxproj file:

		DC2A3CFD2A7819C70077C0D3 /* Release-stable */ = {
			isa = XCBuildConfiguration;
			baseConfigurationReference = 7AFA3C8E1D35360C0083082E /* Release.xcconfig */;
			buildSettings = {
				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
				CLANG_ENABLE_MODULES = YES;
				CURRENT_PROJECT_VERSION = 444;
				DEVELOPMENT_TEAM = 6V53YACS2W;
				DISPLAY_NAME = "Shorebird Example";
				ENABLE_BITCODE = NO;
				INFOPLIST_FILE = Runner/Info.plist;
				LD_RUNPATH_SEARCH_PATHS = (
					"$(inherited)",
					"@executable_path/Frameworks",
				);
				MARKETING_VERSION = 1.2.3;
				PRODUCT_BUNDLE_IDENTIFIER = com.example.flavors;
				PRODUCT_NAME = "$(TARGET_NAME)";
				SWIFT_OBJC_BRIDGING_HEADER = "Runner/Runner-Bridging-Header.h";
				SWIFT_VERSION = 5.0;
				VERSIONING_SYSTEM = "apple-generic";
			};
			name = "Release-stable";
		};

This is usually not what a user wants, so we should probably introduce an iOS validator to check whether these are set and warn the user that the app version in their Info.plist/pubspec.yaml will not be applied and give them steps re: how to fix.

Steps to fix:

1. Go to your Runner (or whatever you've renamed your app to) target in Xcode
2. Click on Build Settings
3. Select "All" and "Levels"
   
4. Search for MARKETING_VERSION
5. Select the green rectangle and delete it
   
6. Do steps 4 and 5 for CURRENT_PROJECT_VERSION

[bryanoltman]

The cause of this problem in the Discord thread that spawned this issue was that FLUTTER_BUILD_NUMBER and FLUTTER_BUILD_NAME were set as user-defined values in Xcode.