Driver: Actually pass -require-explicit-availability{,-target} to frontend jobs

Unless you do this, the flag has no effect when used with the driver;
it only worked in conjunction with -Xfrontend.

Noticed while working on <rdar://problem/58490723>.

Author: slavapestov

lib/Driver/ToolChains.cpp

@@ -192,6 +192,8 @@ static void addCommonFrontendArgs(const ToolChain &TC, const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_typo_correction_limit);
   inputArgs.AddLastArg(arguments, options::OPT_enable_app_extension);
   inputArgs.AddLastArg(arguments, options::OPT_enable_library_evolution);
+  inputArgs.AddLastArg(arguments, options::OPT_require_explicit_availability);
+  inputArgs.AddLastArg(arguments, options::OPT_require_explicit_availability_target);
   inputArgs.AddLastArg(arguments, options::OPT_enable_testing);
   inputArgs.AddLastArg(arguments, options::OPT_enable_private_imports);
   inputArgs.AddLastArg(arguments, options::OPT_enable_cxx_interop);

test/attr/require_explicit_availability.swift

@@ -1,5 +1,5 @@
-// RUN: %swift -typecheck -parse-stdlib -target x86_64-apple-macosx10.10 -verify -require-explicit-availability -require-explicit-availability-target "macOS 10.10"  %s
-// RUN: %swift -typecheck -parse-stdlib -target x86_64-apple-macosx10.10 -warnings-as-errors %s
+// RUN: %swiftc_driver -typecheck -parse-stdlib -target x86_64-apple-macosx10.10 -Xfrontend -verify -require-explicit-availability -require-explicit-availability-target "macOS 10.10"  %s
+// RUN: %swiftc_driver -typecheck -parse-stdlib -target x86_64-apple-macosx10.10 -warnings-as-errors %s
 
 public struct S { // expected-warning {{public declarations should have an availability attribute when building with -require-explicit-availability}}
   public func method() { }