A follow-on to b436825948 where
-m${platform}-version-min was traded for -target. The lit substitution
for %target-clang was relying on -arch and -version-min to specify the
intended platform version to the linker. With the removal of
version-min, only arch was given, so a fallback platform was selected.
For the iPhone simulator, for example, this is iOS 10.99 despite there
being no such simulator for that deployment version. Provide the variant
triple everywhere instead. This has the added benefit of unifying the
special paths catalyst takes.
Fixes rdar://73174820
If we know our deployment target has a new Objective-C runtime, we can
emit fixed metadata for classes with resilient types even if those
types do not appear in the YAML legacy type info.
Fixes <rdar://problem/47649465>.