The _Builtin_float symbols were moved twice, most recently from the OS Darwin library, but previously they were in the embedded @rpath Darwin library. @_originallyDefinedIn doesn't support multiple install names, but it can be replaced with -module-abi-name, and then multiple $ld$previous$ symbols can be used.
Update the Platform and Concurrency magic symbols to use $ld$previous$ everywhere.
rdar://130107191
- Fix one placeholder availability I missed in the previous patch
- Add `visionOS 1.0` availability to work around over-pedantic `@_originallyDefinedIn` diagnostic that started appearing in toolchain builds.
The _Builtin_float interfaces were defined in $@rpath/lib/libswiftDarwin.dylib until macOS 10.14.4 and then in usr/lib/swift/libswiftDarwin.dylib after that. We were trying to use magic-symbols-for-install-name for the first one and @_originallyDefinedIn for the second one. However, @_originallyDefinedIn uses the @available introduced version as the first bound for $ld$previous$ which conflicts with the magic-symbols-for-install-name $ld$install_name$. Eventually @_originallyDefinedIn will need to support multiple install names, but until then just use it as-is and stop using magic-symbols-for-install-name.
Add the missing @_originallyDefinedIn on FLT_RADIX, and match the watchOS/tvOS order between @_originallyDefinedIn and @available.
There was no tvOS 7.0, the first one was 9.0.
rdar://122351557
