[Driver] Disable PCH validation in batch mode, too.

When building in batch mode with a precompiled bridging header, tell
the frontends to disable PCH validation. We have always done this for
incremental, non-batch builds, but forgot to update this check when we
added batch mode.

Fixes SR-11986 / rdar://problem/58455465

Author: DougGregor

lib/Driver/ToolChains.cpp

@@ -403,11 +403,19 @@ ToolChain::constructInvocation(const CompileJobAction &job,
     }
     if (usePersistentPCH) {
       context.Args.AddLastArg(Arguments, options::OPT_pch_output_dir);
-      if (context.OI.CompilerMode == OutputInfo::Mode::StandardCompile) {
+      switch (context.OI.CompilerMode) {
+      case OutputInfo::Mode::StandardCompile:
+      case OutputInfo::Mode::BatchModeCompile:
         // In the 'multiple invocations for each file' mode we don't need to
         // validate the PCH every time, it has been validated with the initial
         // -emit-pch invocation.
         Arguments.push_back("-pch-disable-validation");
+        break;
+
+      case OutputInfo::Mode::Immediate:
+      case OutputInfo::Mode::REPL:
+      case OutputInfo::Mode::SingleCompile:
+        break;
       }
     }
   }

test/Driver/bridging-pch.swift

@@ -48,6 +48,7 @@
 // PERSISTENT-DISABLED-YESPCHJOB-NOT: -pch-output-dir
 
 // RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s %S/Inputs/error.swift -driver-batch-count 2 -enable-batch-mode 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB
 // PERSISTENT-YESPCHJOB: {{.*}}swift{{c?(\.exe)?"?}} -frontend {{.*}} -emit-pch -pch-output-dir {{.*}}/pch
 // PERSISTENT-YESPCHJOB: {{.*}}swift{{c?(\.exe)?"?}} -frontend {{.*}} -import-objc-header {{.*}}bridging-header.h{{"?}} -pch-output-dir {{.*}}/pch{{"?}} -pch-disable-validation