[clang][deps] Include "-cc1" in the arguments

[jansvoboda11]

Summary

To simplify tools consuming dependency scanning results, prepend the "-cc1" argument by default.

[Bigcheese]

lgtm.

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

 }
 
 static std::vector<std::string>
 serializeCompilerInvocation(CompilerInvocation &CI) {
   // Set up string allocator.
   llvm::BumpPtrAllocator Alloc;
   llvm::StringSaver Strings(Alloc);
   auto SA = [&Strings](const Twine &Arg) { return Strings.save(Arg).data(); };
-  SmallVector<const char *, 32> Args;
 
-  // Synthesize full command line from the CompilerInvocation.
+  // Synthesize full command line from the CompilerInvocation, including "-cc1".
+  SmallVector<const char *, 32> Args{"-cc1"};
   CI.generateCC1CommandLine(Args, SA);
 
   // Convert arguments to the return type.
-  std::vector<std::string> Ret;
-  Ret.reserve(Args.size());
-  for (const char *Arg : Args)
-    Ret.emplace_back(Arg);
-
-  return Ret;
+  return std::vector<std::string>{Args.begin(), Args.end()};
 }
 
 std::vector<std::string> ModuleDeps::getFullCommandLine(
     std::function<StringRef(ModuleID)> LookupPCMPath,
     std::function<const ModuleDeps &(ModuleID)> LookupModuleDeps) const {
   CompilerInvocation CI(makeInvocationForModuleBuildWithoutPaths(*this));
 
   dependencies::detail::collectPCMAndModuleMapPaths(

clang/test/ClangScanDeps/modules-full.cpp

 // CHECK-NEXT:       "clang-module-deps": [
 // CHECK-NEXT:         {
 // CHECK-NEXT:           "context-hash": "[[CONTEXT_HASH_H1:[A-Z0-9]+]]",
 // CHECK-NEXT:           "module-name": "header2"
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/Inputs/module.modulemap",
 // CHECK-NEXT:       "command-line": [
+// CHECK-NEXT:         "-cc1",
 // CHECK:              "-fmodule-map-file=[[PREFIX]]/Inputs/module.modulemap",
 // CHECK:              "-fmodule-file=[[PREFIX]]/module-cache{{(_clangcl)?}}/[[CONTEXT_HASH_H1]]/header2-{{[A-Z0-9]+}}.pcm",
 // CHECK-NOT:          "-fimplicit-module-maps",
 // CHECK:              "-fno-implicit-modules",
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[CONTEXT_HASH_H1]]",
 // CHECK-NEXT:       "file-deps": [
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/header.h",
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "header1"
 // CHECK-NEXT:     },
 // CHECK-NEXT:     {
 // CHECK-NEXT:       "clang-module-deps": [],
 // CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/Inputs/module.modulemap",
 // CHECK-NEXT:       "command-line": [
+// CHECK-NEXT:         "-cc1",
 // CHECK-NOT:          "-fimplicit-module-maps",
 // CHECK:              "-fno-implicit-modules",
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[CONTEXT_HASH_H2:[A-Z0-9]+]]",
 // CHECK-NEXT:       "file-deps": [
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/header.h",
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/module.modulemap"
 // CHECK-NEXT:       ],
 // CHECK-NEXT:       "name": "header1"
 // CHECK-NEXT:     },
 // CHECK-NEXT:     {
 // CHECK-NEXT:       "clang-module-deps": [],
 // CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/Inputs/module.modulemap",
 // CHECK-NEXT:       "command-line": [
+// CHECK-NEXT:         "-cc1",
 // CHECK-NOT:          "-fimplicit-module-maps",
 // CHECK:              "-fno-implicit-modules",
 // CHECK:            ],
 // CHECK-NEXT:       "context-hash": "[[CONTEXT_HASH_H1]]",
 // CHECK-NEXT:       "file-deps": [
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/header2.h",
 // CHECK-NEXT:         "[[PREFIX]]/Inputs/module.modulemap"
 // CHECK-NEXT:       ],