gh-138171: Migrate iOS testbed location and add Apple build script (#138176)

Adds tooling to generate and test an iOS XCframework, in a way that will also facilitate
adding other XCframework targets for other Apple platforms (tvOS, watchOS, visionOS and 
even macOS, potentially).

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Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Apple/iOS/Resources/bin/arm64-apple-ios-cpp

@@ -0,0 +1,2 @@
+#!/bin/sh
+xcrun --sdk iphoneos${IOS_SDK_VERSION} clang -target arm64-apple-ios${IPHONEOS_DEPLOYMENT_TARGET} -E "$@"