[ClangImporter] Simply clang-importer creation flags

Currently,  `-direct-clang-cc1-module-build` and `-only-use-extra-clang-opts`
have to be passed together for clang importer creation to succeed.
Missing either will result in error. Simplified the swift-frontend flags
by removing `-only-use-extra-clang-opts` and let
`-direct-clang-cc1-module-build` to do both.

Author: cachemeifyoucan

include/swift/Basic/LangOptions.h

@@ -960,10 +960,6 @@ namespace swift {
     /// DWARFImporter delegate.
     bool DisableSourceImport = false;
 
-    /// When set, use ExtraArgs alone to configure clang instance because ExtraArgs
-    /// contains the full option set.
-    bool ExtraArgsOnly = false;
-
     /// When building a PCM, rely on the Swift frontend's command-line -Xcc flags
     /// to build the Clang module via Clang frontend directly,
     /// and completely bypass the Clang driver.

include/swift/Option/FrontendOptions.td

@@ -1115,9 +1115,6 @@ def target_variant_sdk_version : Separate<["-"], "target-variant-sdk-version">,
 def target_sdk_name : Separate<["-"], "target-sdk-name">,
   HelpText<"Canonical name of the target SDK used for compilation">;
 
-def extra_clang_options_only : Flag<["-"], "only-use-extra-clang-opts">,
-  HelpText<"Options passed via -Xcc are sufficient for Clang configuration">;
-
 def candidate_module_file
   : Separate<["-"], "candidate-module-file">, MetaVarName<"<path>">,
     HelpText<"Specify Swift module may be ready to use for an interface">;

lib/ClangImporter/ClangModuleDependencyScanner.cpp

@@ -167,10 +167,6 @@ ModuleDependencyVector ClangImporter::bridgeClangModuleDependencies(
     swiftArgs.push_back("-module-name");
     swiftArgs.push_back(clangModuleDep.ID.ModuleName);
 
-    // We pass the entire argument list via -Xcc, so the invocation should
-    // use extra clang options alone.
-    swiftArgs.push_back("-only-use-extra-clang-opts");
-
     auto pcmPath = moduleCacheRelativeLookupModuleOutput(
         clangModuleDep.ID, ModuleOutputKind::ModuleFile, moduleOutputPath);
     swiftArgs.push_back("-o");
@@ -307,10 +303,6 @@ void ClangImporter::recordBridgingHeaderOptions(
   // Swift frontend action: -emit-pcm
   swiftArgs.push_back("-emit-pch");
 
-  // We pass the entire argument list via -Xcc, so the invocation should
-  // use extra clang options alone.
-  swiftArgs.push_back("-only-use-extra-clang-opts");
-
   // Ensure that the resulting PCM build invocation uses Clang frontend
   // directly
   swiftArgs.push_back("-direct-clang-cc1-module-build");

lib/Frontend/CompilerInvocation.cpp

@@ -1655,7 +1655,6 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts, ArgList &Args,
     Opts.EnableClangSPI = false;
   }
 
-  Opts.ExtraArgsOnly |= Args.hasArg(OPT_extra_clang_options_only);
   Opts.DirectClangCC1ModuleBuild |= Args.hasArg(OPT_direct_clang_cc1_module_build);
 
   if (const Arg *A = Args.getLastArg(OPT_pch_output_dir)) {

test/ClangImporter/pcm-emit-direct-cc1-mode.swift

@@ -1,6 +1,6 @@
 // Emit the explicit module.
 // RUN: %empty-directory(%t)
-// RUN: %swift-frontend -emit-pcm -direct-clang-cc1-module-build -only-use-extra-clang-opts -module-name script -o %t/script.pcm %S/Inputs/custom-modules/module.modulemap -Xcc %S/Inputs/custom-modules/module.modulemap -Xcc -o -Xcc %t/script.pcm -Xcc -fmodules -Xcc -triple -Xcc %target-triple -Xcc -x -Xcc objective-c -dump-clang-diagnostics 2> %t.diags.txt
+// RUN: %swift-frontend -emit-pcm -direct-clang-cc1-module-build -module-name script -o %t/script.pcm %S/Inputs/custom-modules/module.modulemap -Xcc %S/Inputs/custom-modules/module.modulemap -Xcc -o -Xcc %t/script.pcm -Xcc -fmodules -Xcc -triple -Xcc %target-triple -Xcc -x -Xcc objective-c -dump-clang-diagnostics 2> %t.diags.txt
 
 // Verify some of the output of the -dump-pcm flag.
 // RUN: %swift-dump-pcm %t/script.pcm | %FileCheck %s --check-prefix=CHECK-DUMP

test/ScanDependencies/module_deps.swift

@@ -103,7 +103,7 @@ import SubE
 
 // CHECK: "commandLine": [
 // CHECK-NEXT: "-frontend"
-// CHECK-NEXT: "-only-use-extra-clang-opts"
+// CHECK: "-direct-clang-cc1-module-build"
 // CHECK-NOT:  "BUILD_DIR/bin/clang"
 // CHECK:      "-Xcc"
 // CHECK-NEXT: "-resource-dir"

test/ScanDependencies/module_deps_cache_reuse.swift

@@ -142,7 +142,7 @@ import SubE
 // CHECK: "-emit-pcm",
 // CHECK: "-module-name",
 // CHECK-NEXT: "C"
-// CHECK-NEXT: "-only-use-extra-clang-opts
+// CHECK: "-direct-clang-cc1-module-build"
 
 /// --------Clang module B
 // CHECK-LABEL: "modulePath": "{{.*}}/B-{{.*}}.pcm",