Due to an internal issue, some code from objective-c folder was copied
into objective_c .
Trying to undo that.
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Upgrade apple platform deployment_target versions to fix the cocoapods
push of BoringSSL-GRPC about the following error:
```
ld: file not found: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/arc/libarclite_macosx.a
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
ref: https://developer.apple.com/forums/thread/725300
This also aligns with the versions required by
[protobuf](https://github.com/protocolbuffers/protobuf/pull/10652)
```
ios.deployment_target = '10.0'
osx.deployment_target = '10.12'
tvos.deployment_target = '12.0'
watchos.deployment_target = '6.0'
```
It’s the magic sentence that allows pods dependent on RxLibrary to be
archived correctly by XCode.
It’s less than ideal, and seems arbitrary (why RxLibrary specifically?),
so we’ll try to produce a minimal case and open an issue with it in the
Cocoapods repo.
The examples under <repo_root>/examples now rely on the released
versions. Those under src/objective-c/examples, as well as the tests,
rely on protoc and the plugin as compiled from head.
Tanvi Jagtap