swift

821c2a13 - [Build] Use magic linker symbols to specify an @rpath-relative install name when targeting pre-stable-ABI OSes.

[Build] Use magic linker symbols to specify an @rpath-relative install name when targeting pre-stable-ABI OSes. Magic symbols of the form $ld$install_name$os9.0$@rpath/libswiftCore.dylib tell the linker to use that install name when targeting that OS version. Use these symbols to specify an @rpath install name for all back-deployment libraries when targeting watchOS 2.0-5.1, iOS 7.0-12.1, and macOS 10.9-10.14. rdar://problem/45027809 (cherry picked from commit 4fb99998aefcfd5ded8afb153856e6d4251e05f4)