[Driver] We don't need arclite on pre-10.14 after all

Reverts the effects of df974b2, but keeps the refactoring and nicer
tests.

Author: jrose-apple

lib/Driver/DarwinToolChains.cpp

@@ -208,13 +208,14 @@ static bool wantsObjCRuntime(const llvm::Triple &triple) {
   // When updating the versions listed here, please record the most recent
   // feature being depended on and when it was introduced:
   //
-  // - The hook to override class_getImageName (macOS 10.14 and equivalent)
+  // - Make assigning 'nil' to an NSMutableDictionary subscript delete the
+  //   entry, like it does for Swift.Dictionary, rather than trap.
   if (triple.isiOS())
-    return triple.isOSVersionLT(12);
+    return triple.isOSVersionLT(9);
   if (triple.isMacOSX())
-    return triple.isMacOSXVersionLT(10, 14);
+    return triple.isMacOSXVersionLT(10, 11);
   if (triple.isWatchOS())
-    return triple.isOSVersionLT(5);
+    return false;
   llvm_unreachable("unknown Darwin OS");
 }
 

test/Driver/linker-arclite.swift

@@ -16,14 +16,12 @@
 // IOS_ARCLITE: -o {{[^ ]+}}
 
 
-// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx10.14 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx10.13 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-ios12 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-ios11 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target arm64-apple-tvos12 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target arm64-apple-tvos11 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target armv7k-apple-watchos5 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
-// RUN: %swiftc_driver -driver-print-jobs -target armv7k-apple-watchos4 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx10.11 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx10.10 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-ios9 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-ios8 %S/../Inputs/empty.swift | %FileCheck -check-prefix ANY_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target arm64-apple-tvos9 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
+// RUN: %swiftc_driver -driver-print-jobs -target armv7k-apple-watchos2 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO_ARCLITE %s
 
 // NO_ARCLITE: bin/ld{{"? }}
 // NO_ARCLITE-NOT: arclite