Support stripping Swift symbols

### Description of the problem / feature request:

Support stripping Swift symbols for binaries built for Apple platforms.

### Feature requests: what underlying problem are you trying to solve with this feature?

There's currently no option to allow stripping Swift symbols for binaries built for Apple platforms. Since `xcodebuild`'s ipa exporting supports that (and defaults to `YES`), results in binaries produced by Bazel has a slightly larger size compared to Xcode's.

### What operating system are you running Bazel on?

macOS

### What's the output of `bazel info release`?

release 4.0.0

### Have you found anything relevant by searching the web?

From the `strip` man page:

```
-T
The intent of this flag is to remove Swift symbols. It removes the symbols whose names
begin with `_$S' or `_$s' only when it finds an __objc_imageinfo section with and it has
a non-zero swift version. The future the implementation of this flag may change to match the intent.
```

From the `xcodebuild -h` page:

```
Available keys for -exportOptionsPlist:
...
stripSwiftSymbols : Bool

Should symbols be stripped from Swift libraries in your IPA? Defaults to YES.
```

I found two code paths referencing to code stripping but `-T` is not passed, and passing it via `--stripopt` doesn't take effect.

https://github.com/bazelbuild/bazel/blob/25768512a6c30cdc6af3098078ef02375fd5c914/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java#L1561-L1574

https://github.com/bazelbuild/bazel/blob/ef903e08b270f3fa3c4d36f8122876a892b47087/tools/osx/crosstool/cc_toolchain_config.bzl#L296-L311

Start with the stripping paths in src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java and tools/osx/crosstool/cc_toolchain_config.bzl, then compare them with macOS strip's -T behavior and the reported --stripopt path. Done means Bazel provides an effective way to strip Swift symbols from binaries built for Apple platforms.

Written by the indexing model from the issue text.