Clang enforces a minimum 13.1 deployment target. The driver, API
checker, and various tests assume 13.0 is a valid minimum. Update these
to reflect the actual 13.1 minimum.
Resolves rdar://84177900
Make sure that we add the appropriate rpaths so that the appropriate
_Concurrency back-deployment library can be picked up.
We don't need to update the Swift driver since it uses the C++ driver
as the source of truth to determine if the relevant rpath should be
added or not.
Add `-no-toolchain-stdlib-rpath` flag: the negative version of
`-toolchain-stdlib-rpath`.
Make `-no-toolchain-stdlib-rpath` be the default: use `/usr/lib/swift` as
default RPATH on Darwin platforms instead of toolchain standard library.
Adapted from https://github.com/apple/swift/pull/27206.
tensorflow branch requires the opposite default (use toolchain standard
library as RPATH) because some stdlib modules like TensorFlow do not exist in
`/usr/lib/swift`.
