Revert "Revert "Allow dynamic linking for iOS/tvOS targets.""

This reverts commit 16e10bf.

# Conflicts:
#	compiler/rustc_target/src/spec/apple_sdk_base.rs

Author: cutsoy

compiler/rustc_target/src/spec/apple_sdk_base.rs

@@ -65,7 +65,6 @@ pub fn opts(os: &'static str, arch: Arch) -> TargetOptions {
     TargetOptions {
         abi: target_abi(arch).into(),
         cpu: target_cpu(arch).into(),
-        dynamic_linking: false,
         link_env_remove: link_env_remove(arch),
         has_thread_local: false,
         ..super::apple_base::opts(os, target_arch_name(arch), target_abi(arch))