Fixes getsentry#2954

Without the "archive" command xcodebuild will build with code coverage enabled (`-fprofile-instr-generate` is passed to clang) and that links in the compiler profiling runtime.
This is evidenced by the `__llvm_profile_runtime` symbol being present in the `Sentry` binary with `nm`. The static initializer will hook up profiling and we get a `default.profraw` file when the app exits.

The fix is to use the "archive" command instead, similar to how upstream sentry-cocoa uses it here: https://github.com/getsentry/sentry-cocoa/blob/ddb47781bffd76406f31ab43e66760362585fcd7/Makefile#L82-L83