Rollup merge of #90499 - rusticstuff:macos-target-fixes, r=petrochenkov

Rollup merge of #90499 - rusticstuff:macos-target-fixes, r=petrochenkov

Link with default MACOSX_DEPLOYMENT_TARGET if not otherwise specified.

This PR sets the MACOSX_DEPLOYMENT_TARGET environment variable during the linking stage to our default, if it is not specified. This way it matches the deployment target we pass to llvm. If not set the the linker uses Xcode or Xcode commandline tools default which varies by version.

Fixes #90342, #91082.

Drive-by fixes to make Rust behave more like clang:
* Default to 11.0 deployment target for ARM64 which is the earliest version that had support for it.
* Set the llvm target to `arm64-apple-macosx<deployment target>` instead of `aarch64-apple-macosx<deployment target>`.