macOS: fix link error on x64 with XCode 15

When building the 3.0 branch for macOS x64 with Xcode 15, the link fails with

clang: error: SDK does not contain 'libarclite' at the path '/Applications/Xcode_15.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/arc/libarclite_macosx.a'; try increasing the minimum deployment target
vlckit/VLCKit.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.9, but the range of supported deployment target versions is 10.13 to 14.2.99. (in target 'VLCKit' from project 'VLCKit')

You can reproduce by running ./buildMobileVLCKit.sh -x -a x86_64 -v on branch 3.0, on either Intel or Apple silicon Mac.

This is an issue only when building for x64. Building for ARM64 with Xcode 15 succeeds without this MR.

I understand bumping the macOS deployment version on the 3.0 branch must be considered carefully. Feedback welcome.

/cc @fkuehne