`TargetConditionals.h` was missing several definitions, like
`TARGET_OS_TV` that are part of SDK 10.12 at least. And one that doesn't
seem to occur in any SDK afaict, `TARGET_OS_EMBEDDED_OTHER`.
I added the definitions from SDK 10.12 verbatim and defined
`TARGET_OS_EMBEDDED_OTHER` to be equal to `0`.
I think none of this works if `darwin.Libsystem` is used to build for
linux or iOS though so maybe this needs a more thorough fix?
This reverts 336d82617f1cdd2f5ae77e262afa3f88f5a5e578 because it's no
longer necessary.
84454c3233