Revert "Allow dynamic linking for iOS/tvOS targets."
This reverts PR #73516.
On macOS I compile static libs for iOS, automated using [cargo-mobile](https://github.com/BrainiumLLC/cargo-mobile), which has worked smoothly for the past 2 years. However, upon updating to Rust 1.46.0, I was no longer able to use Rust on iOS. I've bisected this to the PR referenced above.
For most projects tested, apps now immediately crash with a message like this:
```
dyld: Library not loaded: /Users/francesca/Projects/example/target/aarch64-apple-ios/debug/deps/libexample.dylib
Referenced from: /private/var/containers/Bundle/Application/745912AF-A928-465C-B340-872BD1C9F368/example.app/example
Reason: image not found
dyld: launch, loading dependent libraries
DYLD_LIBRARY_PATH=/usr/lib/system/introspection
DYLD_INSERT_LIBRARIES=/Developer/usr/lib/libBacktraceRecording.dylib:/Developer/usr/lib/libMainThreadChecker.dylib:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib:/Developer/Library/PrivateFrameworks/GPUTools.framework/libglInterpose.dylib:/usr/lib/libMTLCapture.dylib
```
This can be reproduced by using cargo-mobile to generate a winit example project, and then attempting to run it on an iOS device (`cargo mobile init && cargo apple open`).
In our projects that depend on DisplayLink, the build instead fails with a linker error:
```
= note: Undefined symbols for architecture arm64:
"_CACurrentMediaTime", referenced from:
display_link::ios::run_callback_ios10::hda81197ff46aedbd in libapp-4f0abc1d7684103f.rlib(app-4f0abc1d7684103f.40d4iro0yz1iy487.rcgu.o)
display_link::ios::run_callback_pre_ios10::h91f085da19374320 in libapp-4f0abc1d7684103f.rlib(app-4f0abc1d7684103f.40d4iro0yz1iy487.rcgu.o)
ld: symbol(s) not found for architecture arm64
```
After reverting the change to enable dynamic linking on iOS, everything works the same as it did on Rust 1.45.2 for me.
In the future, would it be possible for me to be pinged when iOS-related PRs are made? I work for a company that intends on using Rust on iOS in production, so I'd gladly provide testing.
cc @aspenluxxxy
fb92b70f95