"-arch armv7k" is only normally used with a watchos target, but Clang doesn't
stop you from giving a "-miphoneos-version-min" option too, converting the
triple to "thumbv7k-apple-ios". In this case the backend will decide to use
SjLj exceptions, so Clang needs to agree so it can create the correct
predefines.
Fortunately, there's a handy function to make the decision for us now.
llvm-svn: 253355
This patch should add support for almost all command-line options and
driver tinkering necessary to produce a correct "clang -cc1"
invocation for watchOS and tvOS.
llvm-svn: 251706